Well how expensive can character customization be? I don't expect anything beyond 100 cartel coins to be honest. And you're getting like 550 monthly. :l
I would love it to be available for in-game credits as well, though. Especially if it will come with new haircuts.
I know it shouldn't be that mush but still... why? If you are going to implement it make it cost ingame currency. It is ridiculous.