You open the invoice from one of your tools and see the price has gone up again. Or you’re paying for three systems that essentially do the same job, and every Monday someone exports to Excel to stitch them together. Then someone says that line: ”AI makes it almost free to build your own now.”
And suddenly the question is on your desk. Should you build your own system or buy off-the-shelf SaaS?
The short answer is boring but honest: most of the time, you should buy. But there’s one exception worth doing the maths on, and AI has genuinely shifted where that exception begins. Here’s how to think about it.
Buy off-the-shelf for everything that’s common
Most of what a business needs isn’t unique. Accounting, invoicing, scheduling, a simple CRM, payroll. Thousands of companies do exactly the same thing, which is why cheap, mature tools already exist for it.
The price tag is low. According to Bokio’s price list (October 2026), the Swedish accounting software starts at 269 kronor a month, and booking systems and simple CRMs are sold the same way, for a fixed monthly fee, often per user. For that money, the vendor handles hosting, updates, security and backups for you. If you don’t have your own IT person — and most small businesses don’t — that’s a bigger advantage than it looks.
The statistics point the same way, at least when a technology is new. Sweden’s official statistics agency (SCB) found in its survey of IT use in enterprises (November 2025, in Swedish) that among companies using AI, 62.1 percent bought ready-to-use software off the shelf, while 37.1 percent used commercial software adapted by their own staff. That doesn’t prove off-the-shelf is always best. But it shows the market moves buy first, adapt later.
The rule is simple. If there’s a ready-made tool that fits at least 80 percent of your need, buy it.
Build only where your business does something unique
So when is it right to build your own? When the process is the very reason customers choose you.
In his book Dealing with Darwin (2005), strategist Geoffrey Moore splits a company’s work into two parts: what makes you competitive, and everything else that just has to work. Payroll and accounting belong to the latter. Buy them. But if you have a way of working that no standard product can handle, and which is genuinely how you win customers, then it may be worth building.
A simple test: do you bend your business to fit the tool, or the tool to fit your business? If you’re paying staff every week to work around a system’s limits, or gluing together five different services to cover a single process, you’re in the grey zone where custom software can pay off.
What does SaaS cost compared with a custom system?
This is where most people slip up. They compare the monthly cost of SaaS with the one-off price of a build. That comparison is almost always wrong, because you have to think in three to five years, not in a single price tag. It’s called total cost of ownership, and that’s where the real comparison lives.
SaaS gets more expensive every year. According to the price index from Vertice, a SaaS purchasing platform, SaaS prices rose 16.4 percent in the year to June 2026, the highest rate the index has recorded. Add that the per-user price grows as you hire, and that plenty of licences are never even used. In a Gartner Digital Markets survey of 3,484 software buyers (July 2023), 68 percent of fast-growing businesses had regretted a software purchase, against 60 percent on average.
A custom system carries a different cost over time: maintenance. Updates, security fixes, hosting and small adjustments carry on for as long as the system is in use, year after year. You’ll often see 15–20 percent of the build cost per year quoted on development agencies’ websites, but the figure can’t be traced to any study, so ask for the supplier’s own estimate. Run the example anyway: at 15 percent a year, a system that costs £40,000 to build costs around £6,000 a year to keep alive, before you’ve ordered a single change.
So where’s the line? There’s no figure that fits everyone, but three signals say more than the price tag: many users who each cost a licence, large and growing monthly costs for systems that drive your core business, or needing to connect many services to get a single process together. If none of the three applies, off-the-shelf SaaS almost always wins on price, time and risk.
AI has lowered the threshold — but not as much as it sounds
Here’s the new part, and it’s true: AI-assisted development has made building faster and cheaper, especially a first version. The cost threshold that kept small businesses away from custom systems has genuinely fallen.
But the marketing wildly overstates it, and that’s worth knowing before you make a six-figure decision. A widely noted study from the research institute METR (July 2025) had experienced developers work with and without AI tools in codebases they knew well. The developers themselves expected AI to make them faster. In that particular study, the tasks instead took around 19 percent longer with AI.
That doesn’t mean AI is worthless. METR’s own follow-up from February 2026 suggests instead that the effect is hard to measure and varies enormously between situations. Later data hints that developers are now often sped up by AI, but the uncertainty is large. The point is that the gain depends on the task, the codebase and how mature the code is — not on a promise in a sales deck.
AI helps most on narrow, repetitive tasks. It helps least with what actually drives the cost in a real project: integrations with other systems, sensitive data, compliance, security and ongoing maintenance. So plan for AI to shave off part of the right kind of build, not for development to suddenly become almost free.
Translated: AI moves the line for when building your own system is reasonable. It doesn’t erase it.
Where does your data live?
One more thing can weigh heavily, especially if you run a clinic, a law practice or anything else handling personal data. US-owned cloud services can be compelled to hand over data under the American CLOUD Act (2018), which explicitly applies whether the data sits inside or outside the US, so even when the servers are in the EU. According to the European Data Protection Board’s guidelines on Article 48 GDPR (June 2025), such a request from a foreign authority is not in itself a basis for handing over personal data. That creates a legal risk to weigh, particularly for sensitive personal data. For information like patient records, it may be reason enough to choose an EU- or Sweden-based tool, or to build on local infrastructure where you stay in control.
It’s a question of where the data lives, not automatically a reason to build your own. But it belongs in the calculation.
How to decide: build your own or buy SaaS
Don’t start with the question ”build or buy”. Start by listing what you already pay for, and which single process is genuinely your core. Buy off-the-shelf for everything else.
If the core is something no standard product can handle, run a five-year calculation both ways before you decide. A small feasibility study first is cheap insurance against building the wrong thing.
Frequently asked questions
Is it cheaper to build your own now that AI exists?
Sometimes, but less than the marketing claims. AI makes some parts faster, but it doesn’t lower the cost of integrations, security, compliance or maintenance. Calculate the whole project over several years, not just the build itself.
When does switching from SaaS to a custom system pay off?
Usually only once you have many users who each cost a licence, large and growing monthly costs for systems that drive your core business, or have to connect many services. Without those, off-the-shelf SaaS wins on price and risk.
What does a custom system cost?
It varies enormously with what you need. A narrow internal tool costs a fraction of a larger system with many integrations and sensitive data. Always add a yearly cost for maintenance. If you want a figure for your specific situation, it’s best to go through the requirements together before anything is built.
What does total cost of ownership mean?
The total cost over time, not just the price you pay at the start. For SaaS it’s price rises and more users. For a custom system it’s maintenance, hosting and future changes. That’s the figure that decides what’s cheapest in the long run.
Do I have to choose one or the other?
No, and the best answer is usually a mix. Buy off-the-shelf for everything that’s standard, and build your own only for the part that’s unique to your business. That way you get low cost where you can, and control where it counts.
Where does your business stand?
The line between building and buying keeps moving. SaaS prices climb, AI lowers some development costs, and more and more small businesses are starting to ask whether their systems actually help the business. A decision that was obvious in 2024 may look different in 2027.
The important thing is not to start with the solution. Start with the calculation.
If you’re unsure whether to buy SaaS, connect the tools you already have, or build something of your own, we at Monprez can help you make a simple five-year comparison before you spend money on the wrong path.