Use the force and read better. Once it is unlocked for one character, it is 700 cartel coins per character. Also, if you are legacy level 40 (which is when it is the legacy bonus) it is only 300,000 cartel coins, which is fairly inexpensive as far as this type of legacy unlock goes.
edit: also you don't need cartel coins at all if you are legacy level 40, it is 1 million credits.
You better train in the force too. It's 700 Cartel Coins for collections , so that's for your whole account on ( EDIT ) all of the servers.
So I think it is great it is 2100 Cartel coins for the non-legacy unlock and the best method for getting her on your whole account on all servers is , 1 mil credits then the above mentioned 700 CC for the whole of your legacy on all your chosen servers. I think 300 k per character after the initial 1 mil credits is a bit high , but that's only because I have 16 characters.
Overall I'm happy she isn't cheap and that my legacy of over 40 has been worth the effort after losing my 18 legacy levels with the mergers.