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 credits, 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.
fixed, 300,000 cartel coins would be ridiculous