It is quite possible to buy a CD from Amazon and then list it for sale again on Amazon (which costs nothing until you sell it). Anyone can sell on Amazon. I often buy stuff on Amazon that is new but slightly cheaper from a third party seller.
Sounds like a quick route to bankruptcy.
Amazon has your cash until someone else comes along and buys your CD, at which point you will still be out the shipping charges both ways. You'd also have to sell it for less than Amazon to get someone to buy from you rather than Amazon, since you won't be offering the free MP3/streaming version that Amazon does.
BTW, I mostly listen to classical music and Jazz and am very picky about sound quality, which is why I always buy CDs (or flac) and rip my own MP3s for listening on players. Amazon's rips are actually better than most (they use a relatively high bitrate VBR), but ripping them myself gives me complete control over quality, size and tagging.
Many newer CDs have been remastered at higher bitrates, so the sound is much better than older CD versions of the same music. CDs themselves are limited to 16 bit 44,100 Mhz reproduction, but the improved quality of the mastering makes the sound noticeably better. The highest quality MP3 rips are in practice indistinguishable from the CD and preserve the benefits of the remastering.
The same is NOT true of DSD sound on SACDs, which can deliver vastly superior sound to anything you can get from a regular CD, if you have the proper playback equipment. DSD cannot be ripped to regular digital formats, although most SACDs also incorporate a CD (Redbook) layer, which can be, albeit without the 5-1 surround and higher definition of DSD.