A survey did the rounds last week — Retool surveyed a few hundred people who build internal software, and a third of them responded saying they’d already replaced a SaaS tool with something they’d built themselves. This is worth taking with a grain of salt, it’s a company that sells a build-your-own-tools platform asking builders if they like building tools. But the direction matches what I’m seeing and reading, and more neutral voices are saying the same thing. The advent of AI (LLMs specifically) has made “build it in a week” feel real, so the build-vs-buy question is open again.

I’ve spent most of my career on the building side of that question.

About a decade ago I worked on a consumer irrigation product. We built the cloud platform, the web app, the mobile app, the scheduling logic, the communication layer back to the controllers. The software worked. I was pretty happy with it and proud of it. Then it launched, and I learnt the thing that building it had never taught me.

Most of the support requests weren’t software defects. They were people who couldn’t get the hardware to pair, cloud hosting that cost money every month whether anyone logged in or not, customers who expected ongoing help long after a one-off hardware sale. The software turned out to be maybe 5% of the actual product. The rest was operations, support, and keeping the lights on.

This is the part the new build-vs-buy enthusiasm keeps missing. LLMs have handed people who couldn’t build software before the ability to ship it in a weekend, which is new. But shipping is the tip of the iceberg. The cost of ownership sits below the waterline, and you don’t see it until you’ve hit it. Building got cheap. Owning never did.

When you buy SaaS, or even build custom from a trusted partner, you’re not just paying for the features. You’re paying for someone else to run it at 2am, patch it, keep it compliant, and answer the phone when it breaks. Build it yourself and all of that comes back to you, and it doesn’t stop for the life of the product. This cost really needs to be part of the equation, and don’t ignore the opportunity cost of what else you could be doing for your business with that time instead — I read this week someone saying they could replace monday.com to save $2,000 a year, but it would take 200 hours just to write the requirements.

So I don’t think the question has been answered, it’s been moved. It used to be “can we afford to build this”. Now it’s “can we afford to own this for the next ten years”.

It’s not the same call every time. For the commodity stuff — payroll, identity, document storage — buying wins easily. The advantage of building is tiny and the maintenance is real. Harvard Business Review landed in about the same place.

For the thing that actually makes you different from your competitors, owning it was usually the right call anyway. If you’re using the same core platform to run your business as your competitors, your only lever is price. We rebuilt RevenueSA’s tax system rather than buy off-the-shelf, precisely because off-the-shelf couldn’t do what the legislation required. Years later it’s still running and still being enhanced. That’s ownership done well. It isn’t free either. It’s just worth it.

Build it if it’s how you compete. Buy it if it’s how you operate. Either way, budget for the part that starts the day after you ship.