HGG Community Forums

The game itself has over hundreds of thousands of horses, both on active accounts and deactived and quiet accounts. Lots and lots of pixels, stats, showing records, etc.

So its not a "kill" buyer per se. If you sell a horse in auction and no one buys, it goes to the server barn (im guessing eun or administered by the admin im not sure). If the game recognizes a high PT foal, a horse with the potential to have a hugh PT but is not tested - both altered and unaltered - as well as perfect and exceptional create foundations, it will hold them to resell. Both as public sale (2500 or 2750, for an above-average perfect foundation).
If its none of those, then its removed from the game. Essentially this "auction" barn cleans up some of the excess horses that cant necessary be resold or used to give the game a little better performance.
Imagine if we had 8 million pixle ponies still in game but in this auctions barn. The game would be way wayyy slower xD

Hopefully that answers the question, im sure other players will chirp in to correct me ^.^

I remember reading once that the 2750 horses from the Foundation Rescue are better breeders and therefore are more expensive than the other ones. Never tested it though!