First, I've been looking for this to buy with TP for a long time. (not sure if an option now today, but glad to see it in the marketplace).
Now, for the price... Mounts have been extremely overpriced since inception. Even though buying these 9 steeds (account bound) is the same price as buying them for a single toon... its still $150.00 for in game skins.
While I'm sure you have some edge cases, this price seems very silly for 100% cosmo items.
IMHO, at that price, you need to include the following:
All mount dye unlocks (account wide)
Journeyman riders package.
Should likely include ALL store exclusive mounts.
Asking people to drop $150.00 and not gain any content seems like a stretch. Providing more "toys" such as speed boosts and dyes that can be configured, and actually make a gameplay change might tempt some folks to buy this. For a total package like I'm suggesting... I might feel tempted for that price. Asking someone to trade 3 AAA launch titles for some cosmo just ends up with me shaking my head no matter how many times I look at it. Of course this is all IMHO.