I’m curious - if a trainer makes their living off buying fresh, off the track TBs for $2k or less, deals with all of the health issues that come with these OTTBs, gets some basic training into them, takes them to some schooling or rated shows to get the horses started in a discipline, and then sells them for $10K - do you consider this unacceptable? After all, this is a minimum 5x increase in the base price paid for the horse. Or perhaps they got the OTTB for free from the owner or trainer - selling at $10k would be an infinite increase on the base price of $0.
If you now turn around and don’t allow that trainer to take in these horses and maybe turn a profit, you cut out a large proportion of decent, affordable mounts available to amateur owners and you have the problem even more OTTBs with no home to go to.