So, I have a lot of people who come here for the leveling guide. That means a good chunk of my readers are not level 80 yet.
So, I have an important announcement about the cost of your flying mounts (available at level 60 & 70). The 3.2.2 patch changed the price that these skills cost, but you can only get the lower cost at one vendor and not the other. So, if you need to train your level 60 flying mount, or level 70 epic flying mount, mmo-champion says you should go to Hellfire Peninsula.
Jen (one of the commentators) says that Valiance Keep/Warsong Hold is another option for training, with generally the same price as Honor Hold/Thrallmar. So, go with whichever of these two cities (for Horde or alliance) that you have the highest reputation with when you go to buy your mount (until they fix the Dalaran vendor).
Apparently, the Dalaran trainer has the higher prices. The bummer is that the faction discount is different at the two places. So, I guess Dalarn used to have the better faction discount. Right now, the Outland Cities should be a bit cheaper until they get the bugs sorted out.
You guys are correct, we reduced the expert riding skill price in 3.2.2 to 225g. We also changed the faction discounts for the riding skill vendors in Honor Hold and Thrallmar to use Stormwind and Orgrimmar faction.
There are a couple reasons we made this change. First off, we wanted expert riding to be available to more people at level 60. 600g just did not seem like a reasonable expectation for most level 60 players to have when they roll into Hellfire Peninsula. Especially after purchasing your level 60 skills. The second change, regarding the factions just made a lot more sense this way since you will not have any Thrallmar or Honor Hold faction when you enter Hellfire.
Finally, I want to apologize for this change not making the patch notes. We strive to get every change we make into the notes but this one somehow slipped by. Once again, my apologies on that, but hopefully the lower price will help make up for it.