I would rather get nothing for a horse and have comfort in the fact he will not be slaughtered than get $500 for a horse and worry he is going to slaughter. In a few years I won't know where the $500 went. Having a clean conscience, priceless.
I guess I see horses as companion animals. Would you sell your dog to the meat man for $50? I don't see a horse as any different. But I know other people do.