I was just reading on the [url=http://www.worldofwarcraft.com/info/basics/mounts/flying.html]WoW[/url] site that Artisan training to be able to fly an epic mount will cost 5000gp.  Add to that the 800g for Expert training and 200g for the mount itself and you're looking at a grand total of 6000g!  Of course you'll need to add 100g to that if you want to have a normal flying mount to ride in the meantime.  But what's 100g?  Just a drop in the bucket!