Where was anyone suggesting that this person should have picked up a rescue or some grade POS?
From the comments in the other thread (Free Speech My Ass).

The remarks about how "insane" it is for that man to pay that kind of money for a horse "just for trail riding" tells me many don't feel the mare is worthy of that sort of investment. There is no other logical explanation for that line of reasoning. How strange is it that many don't see the value in paying good money for a top quality horse, yet will invest thousands into the maintenance of a rescue that will never be a productive member of horsey society?

Since we don't know all the details (or what exactly the buyer was looking for), we shouldn't criticize the buyer (i. e. "more money than brains"). Absolutely, there are plenty of horses available out there (here and in Australia) of all levels of quality, ranging in price from free to the big bucks. However, if a buyer is looking for a certain quality or type, it's not unusual at all for them to pay good money for it. A high quality horse (of any breed) is difficult to find, if your selection criteria is high enough. Evidently, this mare fit exactly what the buyer was looking for, regardless of her price or her intended purpose.