Legacy System Replacement Cost in Australia (2026)

What Drives the Cost of Replacing a Legacy System

Legacy system replacement is quoted at a fixed price after a technical audit — the price you see at the start is the price you pay. Understanding what drives that price helps you build an accurate internal business case before engaging anyone.

The four variables that matter most:

• System complexity — the number of distinct workflows, user types, and business rules embedded in the legacy code. A single-purpose portal is simpler than a platform serving three user groups with separate permissions and views.
• Data volume and quality — migrating 10,000 clean records is straightforward. Migrating 1,000,000 records from a Microsoft Access database with 16 years of accumulated inconsistencies requires careful transformation logic and multiple validation cycles.
• Number of portals — each distinct user-facing interface (staff portal, client portal, management dashboard) adds scope. Most projects require one to three portals.
• Third-party integrations — connecting to Xero, MYOB, a payment gateway, or an industry-specific platform adds complexity and testing time.

Cost Ranges by Project Tier

Real AUD ranges based on delivered projects, not estimates derived from international benchmarks.

Technical Audit: $2,500–$5,000 (1–2 weeks)

A standalone audit of your existing system — not a sales call. You receive a written report covering data model mapping, workflow documentation, risk assessment, migration complexity, and architecture recommendation. The audit concludes with a fixed-price quote for the full project. The audit fee is credited against the project if you proceed.

Core Modernisation: $25,000–$60,000 (6–10 weeks)

A complete replacement with a modern cloud platform. Includes one primary portal, full data migration with zero data loss, all core business logic rebuilt, cloud hosting with managed backups, role-based access control, and full source code handover. Suitable for single-portal systems with up to several hundred thousand rows.

Full Platform: $60,000–$120,000+ (10–16 weeks)

Multi-portal platforms with complex data migrations, third-party integrations, and advanced workflows. Suitable for systems with multiple user types, high data volumes, or significant new capability requirements. The Drill Guys project — 1M+ rows, three portals, 8 weeks — sat at the lower end of this tier.

The Replace vs Retain Decision

The cost of replacement is only meaningful when compared to the true cost of retention. Most legacy system owners significantly underestimate what running an old system actually costs per year.

At the low end, that is $23,000/year. At the mid-range, $70,000+/year. A $40,000 replacement project that eliminates most of those costs pays for itself in under two years — and delivers a system the business owns outright with no ongoing vendor fees.

Why AI-Accelerated Delivery Changes the Maths

Traditional legacy replacement projects from Australian enterprise agencies often quoted 6–12 months. At that timeline and price, the business case was difficult for an SMB to justify. AI-assisted development compresses those timelines to 6–12 weeks for the same quality of output — making the economics work for businesses that previously could not justify the spend.

Getting a Reliable Quote

The only reliable way to get an accurate fixed price is through a technical audit. Quotes given without auditing the system are guesses. We audit first — mapping every table, workflow, and dependency — before providing a price we commit to. No hourly billing, no scope creep. Start with a free discovery call and we will tell you whether an audit makes sense for your situation before you spend anything.