Repair costs astronomical?

Sent my iPad Pro in for a repair through the major German electronic chain store from where I purchased it from (they then send it to Apple). Background info: It´s about two and a half years old. I updated it with the last available update about 8 weeks ago. The iPad itself was working fine immediately afterwards, but then I noticed that the reloading icon disappeared and there was a rapid power loss. Tried all the standard procedures, including using a new recharge cable to try and get it to recharge, but everything failed and the power drained to zero.

So off it went, with a description of the power problem. Later on, I get a letter stating that the repair would cost me €505.23 (!)...without any description about what the problem is or what needed to be done. The repair price for a power problem seems crazy and dubious to me. Seriously, I can purchase a brand new iPad (granted, a more basic one) for €379. So my question is: are repair costs carried out by Apple for power related problems really this high in general? The letter also stated that they would also "ecologically" scrap it for me for no cost, or return it to me. I´m having it returned. I've got a friend of mine who is itching to take it apart and find the problem out himself.