This is all highly speculative and doesn't include several costs (like marketing as you mention) but also revenue streams (merchandise, videogames, LEGO sets, Star Wars stuff in the theme parks... literally everything with the Star Wars name on it etc. This is and always has been a huge part of where Star Wars made it's money as a franchise, all the way back from the original movie).
Also the acquisition of Lucasfilm is not a cost in the same way as the production budget of a movie is. Lucasfilm's value is added to that of Disney as a company. Sure that value may now be lower perhaps than what Disney acquired it for but that's neither here nor there as long as they're not selling it. Lucasfilm as an asset still exists and is part of Disney.
I do not for a second believe that TFA with a 2 billion box office only made Disney 37 million in profit and I have no idea what you mean by "still have to pay back investors".
