What it costs to upgrade, take over or look after a bespoke business system
"How much will it cost?" is the first question most people ask about their software, and the honest answer is "it depends". This guide sets out what it depends on, the starting price of each first step, and the running costs worth budgeting for.
Why there's no single price
Two systems that look alike from the outside can be very different underneath. One has tidy code, automated tests and a deployment anyone can repeat. Another has years of rushed fixes, no tests and a live server nobody dares touch. The work to upgrade or take over each one is not the same, and any price given without looking inside is a guess.
So every piece of work starts with a paid first step: a review that looks at the real system and produces a written, costed plan. The table below shows that first step and its starting price for each service.
Starting prices for each first step
| Service | First step | Starting price |
|---|---|---|
| .NET modernisation and upgrades | Upgrade audit | from £1,500 |
| Taking over an orphaned system | Takeover audit | from £1,500 |
| Care plans | Paid onboarding review, then a monthly plan | Essentials from £195 / month; Business from £450 / month; Priority quoted |
| AI integration | AI opportunity review | from £1,500 |
| SaaS and MVP development | Discovery and scope | from £1,500 |
| Technical due diligence | Supplier or platform review; acquisition or investment review | from £1,500; from £2,500 |
| Real-time data for live events | Technical review | from £1,200 |
Some follow-on work also has a published starting point: an AI pilot on one use case from £6,000, an MVP build from £12,000, ongoing support for a new product from £900 a month, and a keep-current plan for an upgraded .NET application from £450 a month. Everything else, such as the upgrade itself or stabilising a system you've taken over, is estimated in the first step.
What drives the cost
These are the things that make the biggest difference to the price of an upgrade, a takeover or ongoing care:
- Size of the application. The number of screens, reports, background jobs and business rules. More code means more to check, change and test.
- Number of integrations. Every connection to a payment provider, accounting package, email service, supplier feed or other system is something that can break during an upgrade and has to be tested end to end.
- Automated test coverage. A system with good automated tests can be changed with confidence. Without them, tests often have to be written around the critical paths before anything changes, and that work is part of the cost.
- How far behind the framework is. Moving from .NET 8 to .NET 10 is usually a much smaller job than migrating from .NET Framework. Old third-party packages with no modern version need replacing, which adds work.
- Hosting. Staying on the same kind of server is simpler than moving to containers or the cloud at the same time. Ageing servers, such as Windows Server 2016, can force the hosting question whether you planned for it or not.
- Data migration. If the database has to move, change version or change shape, the data has to be moved and checked carefully, and that is often where the surprises are.
- Documentation. Notes on how the system is built, deployed and backed up save time. Where there are none, they have to be worked out from the code and the servers first.
- How much is known. If the source code, passwords or hosting accounts are missing, recovering them comes before anything else. See what to do when your developer has left.
Why the first step is paid
An estimate given after a short phone call or a look at the website has to cover the unknowns somehow. Either it's padded to allow for problems that may never appear, or it's optimistic and the extra cost turns up halfway through the work. Neither helps you budget.
A paid review removes most of the guesswork. It looks at the real code, packages, hosting, data and integrations, and produces a written report with the risks and a costed, staged plan. The rest of the work is then estimated from real scope. You keep the report whether or not I do the follow-on work, so it's useful even if you take it elsewhere or decide to wait.
Why a rewrite usually costs more
When a system feels old and fragile, starting again can look like the clean option. In practice a rewrite is rarely the right first answer:
- It has to rebuild every feature, report and business rule before it is as useful as the system you already have.
- Many of those rules aren't written down anywhere except in the code, so they get missed and rediscovered the hard way.
- You pay to run and support the old system until the new one is ready.
- The cost lands up front, with nothing to show for it until the switch-over.
A staged upgrade spreads the cost and the risk. Each stage is tested and released while the system stays live, and each one leaves you better off even if the next is paused. Sometimes the review does find that part of a system is beyond saving, and then replacing that part is the honest recommendation. It's rarely all of it.
Ongoing costs to budget for
The one-off work is only part of the picture. A bespoke system has running costs every year, and budgeting for them avoids an expensive scramble later:
- Hosting: the servers or cloud services the system runs on, plus backups and monitoring.
- Maintenance: security patches, dependency updates and small fixes as browsers, payment providers and other services change around you.
- Framework upgrades: every framework version eventually loses support. .NET 8 support ends on 10 November 2026, and .NET 10 is supported until November 2028. Planning each upgrade costs less than rushing it at the deadline.
- AI usage: if you add AI to an existing system, the AI provider bills per request. A pilot measures that cost on real work, so you know the monthly figure before rolling out.
A care plan rolls hosting, monitoring, patches and a monthly allowance for fixes into one predictable monthly fee, with framework upgrades scheduled on the Business plan. Work outside the plan is quoted before it starts.
Need a hand?
I've built and supported bespoke business systems for 30 years, including a job, stock and invoicing system that has been in daily use for more than 11 years. If you want to know what your system will cost to upgrade, take over or look after, the first step is a .NET upgrade audit, a takeover audit or a care plan, depending on where you are. Each gives you a written plan and real numbers before you commit to anything more.