There are 2 other ways to unlock species in game:
1- Level up one character to level 50 (or 55 now?) and that species will be unlocked to be used with any future class you start after this
2- buy the species fo 1.500.000 credits in game with a level 50 character. (Im really not sure about the level of the character, but there is a way to do this in game)
Neither of them are as easy as buying in the Cartel Market but at least they are inexpensive on you real life pocket.
Obs: I have to say that I have a subscription and that I do not know if this works for non subscribers.