I think your problem is arising from your approach to it. It sounds like you see it as a less regulated version of shop, rather than a more regulated version of eBay.
In a shop, you might buy the cheapest option, and be fairly confident it will work.
You wouldn’t, or at least shouldn’t do that on ebay.
Nah. Where I live, eBay is a synonym for buying used stuff. I know thats not quite true, but this is how eBay was conceived, and is still perceived around here. We have a more local service for that, which is fine for finding something which doesnt need to be new... But at least a few years ago, there was a clear difference between amazon.de and say willhaben.at :-) Maybe that has changed even more, I wouldn't know. I basically gave up on looking up stuff on amazon.
In a shop, you might buy the cheapest option, and be fairly confident it will work.
You wouldn’t, or at least shouldn’t do that on ebay.
It’s the same on amazon