Someone once said bikes are the currency of drug addicts.
Lots of stories of people finding their stolen bikes for sale on line. Most thieves don't even bother to disguise them, just sell them outright. Pawn shops are another fencing ground.
I occasionally come across $3k new, year old full suspension bikes on CL for $500 or less. Seems like the picture is usually in front of a storage unit. The ads rarely stay up more than a day so my guess is they sell in hurry to people who ask less questions than I do.
Unfortunately the market is there.
Would also say lots of cheaper bikes are just dumped somewhere else.