Legacy software modernization for a small business can cost $3,000 to $30,000 for a focused, phased project. An assessment may cost $1,000–$3,000. Stabilizing or isolating one risky component may cost $3,000–$9,000. Modernizing a substantial workflow can cost $9,000–$30,000. Replacing a broad business system may cost $30,000–$75,000 or more.

These planning ranges use Vertinus's published rate of $49.99 per hour. Legacy work is difficult to price from screen count because undocumented rules, fragile dependencies, data quality, operational risk, and migration often create more work than the replacement interface.

Quick answer: a 20–60 hour assessment is about $1,000–$3,000; 60–180 hours of focused stabilization is about $3,000–$9,000; 180–600 hours of phased modernization is about $9,000–$30,000; a 600–1,500 hour replacement is about $30,000–$75,000.

Typical modernization price ranges

Assessment and plan: 20–60 hours

Estimated Vertinus cost: $999.80–$2,999.40.

An assessment may inventory business workflows, code, infrastructure, data, integrations, users, recovery, security, known failures, ownership, and replacement options. The output should recommend a first boundary with estimated hours and risk.

Focused stabilization: 60–180 hours

Estimated Vertinus cost: $2,999.40–$8,998.20.

This range may fit improving backups, documenting deployment, fixing a dangerous failure, adding monitoring, isolating an integration, upgrading one dependency, creating a supported export, or putting a safer interface in front of a stable legacy core.

Phased workflow modernization: 180–600 hours

Estimated Vertinus cost: $8,998.20–$29,994.

This range may replace one complete workflow, introduce a supported database or application interface, migrate active data, connect surrounding systems, and operate old and new components during transition.

Broad system replacement: 600–1,500+ hours

Estimated Vertinus cost: $29,994–$74,985 or more.

This range can apply when the legacy application controls several departments, many record types, years of history, financial processing, customer access, field work, reports, documents, and critical integrations.

Modernization is not always a rewrite

Modernization can mean:

  • Documenting and stabilizing the existing system.
  • Upgrading unsupported runtime, framework, database, or infrastructure.
  • Adding monitoring, backups, recovery, and deployment controls.
  • Wrapping stable legacy functions behind a supported application interface.
  • Replacing one risky workflow while leaving other components in place.
  • Moving data into a supported database or platform.
  • Buying an established replacement and migrating to it.
  • Building a new application in controlled phases.

The safest and least expensive option often preserves stable behavior while removing the most consequential dependency first.

The broader legacy software modernization guide compares common paths and rollout risks.

The nine biggest cost drivers

1. Business scope

A single data-entry utility is simpler than software controlling customer records, orders, inventory, scheduling, production, billing, and reporting.

2. Availability of source code and environments

Readable source code, build instructions, version history, test data, and a working nonproduction environment reduce uncertainty. Missing code or vendor-only access can force a different strategy.

3. Undocumented business rules

Legacy behavior may exist only in code, database triggers, reports, spreadsheets, employee workarounds, and long-serving staff knowledge. Recovering those rules takes interviews, observation, data analysis, and testing.

4. Data condition

Stable identifiers, valid relationships, and known field meanings simplify migration. Duplicates, orphaned records, mixed encodings, inconsistent dates, free-text status, and missing history add profiling and correction.

5. Integrations and dependencies

Accounting, payments, devices, files, email, suppliers, customers, scheduled jobs, proprietary protocols, and downstream reports may depend on exact legacy behavior.

6. Operational downtime tolerance

A tool that can be offline for a weekend is simpler to replace than a system required continuously across locations or shifts. Parallel operation and staged cutover add work but reduce risk.

7. Historical record requirements

Migrating only active records is less expensive than making every historical transaction, attachment, audit event, and report fully available in the new application.

8. Security and regulatory context

Sensitive customer, employee, payment, health, safety, or regulated records require qualified guidance, stronger access design, validation, retention, and evidence.

9. Testability

Existing automated tests and reconciled outputs reduce risk. When no expected behavior is documented, representative scenarios and comparison reports must be built before old functionality can be retired safely.

Three example estimates

Example 1: stabilize an unsupported office application

A small desktop application runs on one aging computer and stores customer and job data in a local database. The business needs verified backups, a supported export, documented installation, monitoring, and a plan for later replacement.

  • Assessment and recovery test: 14–24 hours
  • Export, backup, and documentation: 18–35 hours
  • Environment stabilization and monitoring: 18–35 hours
  • Testing and transition plan: 10–20 hours

Planning total: 60–114 hours, or about $2,999–$5,699.

Example 2: replace one legacy workflow

An older application handles customer intake, quoting, and job creation. The new phase will replace those functions with a web application, migrate active records, and feed approved jobs back to the existing scheduling and billing components.

  • Discovery, rule recovery, and prototype: 30–55 hours
  • New workflow and administration: 90–170 hours
  • Legacy integration and active-data migration: 50–100 hours
  • Comparison testing, parallel use, and rollout: 40–80 hours

Planning total: 210–405 hours, or about $10,498–$20,246.

Example 3: replace a multi-department system

A business depends on a custom application for customers, orders, inventory, scheduling, documents, invoicing, and management reports. It has fifteen years of data, several file integrations, and no automated tests.

  • Assessment, rule recovery, and architecture: 80–150 hours
  • Core application workflows: 300–600 hours
  • Integrations, reports, and administration: 150–320 hours
  • Migration, reconciliation, parallel operation, and rollout: 150–350 hours

Planning total: 680–1,420 hours, or about $33,993–$70,986.

These examples illustrate likely scope. They are not fixed packages or quotes for an unseen system.

Why all-at-once rewrites fail

A broad rewrite asks the team to rediscover every rule, rebuild every workflow, migrate every record, reproduce every integration, train every user, and switch operations at one moment.

During the long build, the business and old system keep changing. Missing edge cases appear late, and users cannot validate the application until most of it exists.

Prefer a boundary that can be built, reconciled, and used independently. Each phase should reduce operational dependence on the legacy system even if later phases pause.

Buy a replacement before building one

Evaluate established products when the underlying workflow is standard. Subscription software may provide mature security, mobile use, reporting, integrations, and product support for less than a custom replacement.

Include migration, configuration, integration, training, subscriptions, contract terms, and exit costs in the comparison.

Custom development is justified when an important business-specific workflow creates measurable value or when available products cannot support the required operating model without expensive workarounds.

What an assessment should deliver

  • A map of business workflows and critical users.
  • An inventory of code, infrastructure, databases, jobs, and integrations.
  • Ownership, access, backup, recovery, security, and support risks.
  • Data profile, export options, history needs, and migration constraints.
  • Candidate paths: stabilize, upgrade, wrap, replace with a product, or rebuild.
  • A recommended first boundary with assumptions and exclusions.
  • Estimated hours, operating risk, dependencies, and verification method.
  • A fallback if the preferred path proves infeasible.

Do not pay for an assessment that produces only a generic recommendation to rewrite everything.

What a modernization estimate should include

The scope should identify preserved and replaced behavior, source access, environments, data, integrations, history, reports, security, testing, parallel operation, cutover, rollback, training, decommissioning, monitoring, and support.

Vertinus provides written scope and estimated hours before development. Work is billed at $49.99 per hour up to the approved estimate; added requirements are estimated separately.

What Vertinus needs to estimate the first phase

Describe what the software controls, who uses it, what would happen if it stopped, where it runs, who has source and database access, which systems exchange data, and which failure creates the greatest business risk.

Useful evidence includes redacted screenshots, exports, architecture notes, error logs, vendor documents, and a demonstration of one important workflow. Do not send passwords, production credentials, or unnecessary sensitive data.

Price the next risk-reducing boundary

Legacy modernization commonly costs $3,000–$30,000 when performed as focused, phased work. The right first investment makes recovery, ownership, data access, or one critical workflow materially safer.

Tell Vertinus what the legacy system runs and what would happen if it stopped. We will identify the smallest useful assessment or modernization boundary and reply with estimated hours at $49.99 per hour.