Ekhem, You are forgetting that SWTOR was in development for many years and EA invested huge amounts of cash on this projects that they didn't get back yet.
After you ship single player game (and even multiplayer that is not mmo) there are no additional costs for the company or at least they are low (in comparison to mmo project).
With mmo you have to count in that even with layoffs EA still have to pay for developing new content, keeping support and maintaining server infrastructure and its not cheap. You simply need x subscriptions to have any profit otherwise you are generating monthly loss even if there is noticeable income.
AFAIR they said before release they need at least 300 000 paying accounts to have any profit.