I can't imagine any of the mounts becoming easier to obtain through the Black Market, to those throwing a panic attack over their hard-earned mounts suddenly being "easier" to obtain. Think about it. There's a lot of people on your server, more than you care to realize. There's only going to be sold one mount at a time, and everyone will be bidding on it. No doubt the 20k starting bid will be nothing compared to the actual bidding wars that will go on, and I assure you there's a lot of people sitting on +50k gold willing to spend almost every coin on such a rare mount. People will begin to hoard gold for the single purpose of bidding. It will be seriously hard to get something from such an Auction House.