The functionality may be similar, but the scale is completely different and shouldn’t be ignored. Building a machine that cooks 1 pancake every 5 minutes is a fun project for precocious college students; designing a system capable of cooking 10,000 uniform pancakes per minute is a feat of incredible industrial engineering.

I'm talking about R&D specifically, not infra folks.

But let's say designing for scale is 100 times harder than a taxi app for just one national taxi service. Based on my 23 year career in trenches I seriously doubt that's the case, but let's be generous.

That would net us into ballpark of €60M expense. Non-negligible, but it translates into a hundred developers pulling €100k a year for 6 years, still at least an order of magnitude below Uber.

Very obviously it does not scale anywhere near linear. There has to be a severe case of diminishing returns in technical hiring.

So did early Uber. Famously, the contractors were Spanish-speaking, so FTE engineers #1-5 had Spanish-English dictionaries on their desks to understand the code.

fair, but also a lot of Uber's business model is leveraged on top of the basic platform.

What does that mean?

It means that the functionality of the app that immediately comes to mind is only one of the many ways in which they lose an extraordinary amount of money.