it's not really "overpriced" if that's what someone was willing to pay. SoSofts can be pretty desirable MOC, and Gusty is a popular pony.
Exactly what I was going to say.
Did it sell for more than expected, more than the market normally places it and more than what most people would pay for it? Yes it certainly did...by 3 times!
However a pony is "worth" what it sells for. If she sold for $50 then thats what she was worth to the winner and a minimum of at least one other person. If she sold for $300 likewise. You never know what forces the price up - someone looking for that last collection completer, someone after a grail - either way for the winner the pony is worth what they have bid.
Congrats to the seller and well done to the buyer