Patch 3.2.2 Mount Changes
Apparently, the price to train the riding skills has been slightly changed in patch 3.2.2 and the first rank of flying mount is now considerably cheaper. (Thanks to iridius for the tip)
* Expert Riding (150% Flying) now costs 250G (Down from 600G)
The problem is, this change doesn't seem to affect all trainers. Trainers in Hellfire Peninsula will offer you the mounts at a reduced price but Hira Snowdawn in Dalaran will just try to steal all your money and will ask for the pre-3.2.2 prices. This isn't a reputation discount, I checked with different characters including RAF alts with no reputation like this one. (But keep in mind that you get a discount based on your Stormwind/Orgrimmar reputation instead of the Honor Hold/Thrallmar one in 3.2.2)