While it's a curious move on the surface, it effectively restricts players from Europe purchasing their Pandaren Monk and Lil' K.T. from the US store where the pets are cheaper at $10 compared to €10 or £10 in the EU (roughly $15). Interestingly enough, the pets are priced at ₩12,000 in the Korean version of the store, which is about the same price as in the US ($10.3). It's unclear why the European version of the pets -- along with a few other Blizzard store items -- are more expensive, a fact that makes Turpster huff and puff and blow Azerothian houses down.
Obvious business reasons aside, it also creates a minor inconvenience for people who would like to give the pets as gifts to players in other regions. However, considering that many vanity pet codes have been regional in the past, such as those given away during Blizzard special events, it's not a surprising move. Then again, this whole foray into microtransactions was a bit of a surprise, so we've learned to never underestimate those folks from Irvine.