When people are trying to sell horses you're not likely to find them posting health issues, vices or training issues. They want to sell the horse. Some people will, but most won't. So it's up to the buyer to do things like vet checks and if they don't know horses, bring someone along that can see through anything a 'bad' buyer might try to pass off.
In this case, there might be things going on because of horrible breeding. And as far as the price doesn't matter what she's really worth. A seller is going to try and get as much as they can. There are a lot of horses out there not worth 1/4 of the asking price, yet there are plenty of people out there willing to pay.
Some people don't know any better not to pay such a price for a horse that's not really worth it. It wouldn't surprise me in the least if they got 350.00 because it's a novelty type horse. I doubt anyone with decent horse knowledge would pay that but you never know.