Do you know any alternative to glass back cover that's harder to scratch and isn't too expensive?
Glass is harder to scratch than metal... my samsung with glass on the back is the first phone which still looks the same after a year. I don't have any protective case on it or anything, because i'ts all glass, so it won't scratch unlike metal and plastic, which are quite easy to scratch.
There are 2 reasons why people don't put their phones display down:

• they have shitty phones with shitty glass (not gorilla glass)
• they are overly careful because it's a display... they don't care so much about back cover

You're not the first person I heard complaining about this. Not a single person I heard complaining complaining has ever used an expensive phone with glass back.