If you've ever worked in an engineering team in a regulated market, this is commonplace. Regulators aren't here to ensure you, the regulated party, can make money. They are in place to ensure the marketplace as a whole is fair(ish). Compliance is costly.

> they're asking Apple to spend all the engineering time developing APIs, xCode, etc. for free

I find such arguments more than absurd,

1. They have no issue doing that on macOS

2. Apple needs third party developers as much as the other way around. They are not doing this for free, they would sell a lot less devices if third party Apps weren't supported.

They're already pocketing 17% + the cost of every iDevice they sell. You're seriously going to say that's not enough?

Which can be paid for by selling hardware devices.

The world does not own Apple any level of profit.

They already regulate how high credit card interchange fees can be, even though the banks had to spend money on building and maintaining the credit card infrastructure. They also regulate how high mobile roaming costs may be, even though cellular networks have cost hundreds of billions to build. Of course, they're only doing that because the interchange fees and roaming charges were abuse of market power and in no proportion to the cost of actually providing the service. Just like Apple's Core Tech Fee is.

So there's not going to be any problem with putting limits on the amount of money Apple can leech. Nor will there be any downside to doing it. Apple will not put any less effort into their platform or tooling even if such limits were in place. Nor is there any chance that Apple will abandon the EU market.

(If Apple was charging a nominal fee instead of a punitive one, they'd have a much better argument. But for Apple, it's not about the money they make from the technology fee. It's about making sure that the regulation can't actually achieve its purpose of promoting competition, because Apple will have smothered the competition in the crib.)