In Arizona recently, I bought a 2 year old, green broke, registered Paint filly for $400. I bought a fully trained, sweepstakes nominated Arabian mare with experience in endurance racing for $1200.
Not much of a market now for an adult horse that may try to kill you...
BTW - I later GAVE the paint filly to a woman who trains horses. A year later, she is a beautiful young horse being ridden daily.
Lots of OK riding horses show up for free on Craigslist...