100k Eur is high salary for a dev. A unicorn who knows they are one, won't agree to that salary, but would for 150k or 200k.

Europe, probably

I'm picking a random salary that's not too high that lower comp countries/industries will reject, and not too low that higher comp countries / industries will reject, and then doing math on those.

You can then take my numbers or math and plug in YOUR comp rates. But the TL;DR I've seen is many people never even do napkin math like this on ROI.

These numbers are actually WAY LOW for silicon valley. If I was doing the ROI for an Amazon employee I'd start with around 350 for an SDE all told for entry level and half a mill for one with a few years experience.

But they're also way high for other places. And just right.

The point is how to do the math not the ballpark. Also that even at 100k for a dev it's maybe a wash depending on your time horizon.

That “main engineering effort” will go on forever. People neglect to note that everything is constantly changing. Just like the roof on your house, if you don’t upgrade your components regularly, eventually you will face a huge rewrite when that thing your ancient home-made infrastructure relies on is no longer supported or is no longer updated to support the latest thing you need for your SaaS.

You can’t avoid this cost. Some people refer to it as technical debt, but I think more accurately it could be called “infrastructure debt”. Platform providers maintain the infrastructure debt for you - this is what you pay them for. And they do it with tremendous economies of scale. Unless your scale is truly enormous - like Meta, for instance - it isn’t worth build your own infrastructure.

Sure. We have around 10 of those. It’s a significant boon to the project for them to do nothing.