No, it is not even rent. It was one service provided as part of the "Quick start program"
From:
https://developer.apple.com/programs/universal/
"As part of the program, you’ll have limited access to a Developer Transition Kit (DTK), which will be shipped to you, for developing and testing your Universal apps. The DTK is owned by Apple and must be returned."
(...followed by a link to a very clear set of terms and conditions - that have been quoted here several times already - that made it
very clear that the DTK had to be returned on demand and if it broke you got to send back both parts, and that the fee was non-refundable).
No, they're
gaining €414 because
they were never promised a single cent back. It was a voluntary, good-will "gift" from Apple (albeit one they'd probably mitigate with extra Mac sales). Trouble is, you start from the false premise that developers were somehow entitled to a refund of their $500 and turn that into all sorts of nonsense. Or are people suggesting that Apple should have sent a
$600 thank-you to people in Europe, but only $500 to US developers?
The Quick Start program wasn't obligatory and there was plenty of free information on how to get your code to the stage where it should "just compile" as soon as you got your hands on a M1.
If you didn't gain significantly more that $500 in sales by being a month or two ahead of the game in having a Universal version of your app, then you made a bad business decision. Own it... and if you enter into
business-to-business deals (which lack many of the consumer protections that apply in many places, certainly the EU) without properly reading the contract then learn, quickly, or risk getting into
real trouble.
It's certainly more than any other manufacturer would have offered to rank-and-file developers paying the princely sum of $100 a year (which is peanuts by developer program standards). Apple didn't
need the DTK program at all - they could have just invited key developers like MS, Adobe et. al. to play with their (presumed) handful of pre-production M1 lash-ups. It must have cost them a small fortune to do a tiny run of the DTK, I doubt that they made much money from the program. Turns out that huge tranches of x86 software worked perfectly well in Rosetta, anyhow...