If, by chance, your first toon is not human, it is worth is to save up 500k to buy the unlock.
Humans that reach 50, or buy the unlock, gain +100 Presence to all toons within the legacy.
Also, each companion within each of the 8 stories will give a +10 Presence boost across all toons.
Presence affects how well your companions fight, so at lower levels, your companion can almost solo content.
The benefit is less noticeable as you gain levels, but it still helps.