In the intetest of fairness the "billion dollar game" is funny but it is not applicable in almost any case wherw it is used in reference over the last few days.
Businesses dont work that way. Businesses work off 'productivity' which might equate 1 work hour to 'x' thousand dollars of in-game revenue.
At that point, the amount of money beijg brought into the game is far less relevant as you are always compared to you productivity number, if it isn't hitting targets then you need to improve what you're doing.
What this means is that equating a days worth of in-game take to a salary is irrelevant. When they say expensive they mean it could take 1000 hours of work time, that isnt $50,000 if the people working on it are making $50 an hour, thats millions and millions of dollars that they can't directly and immediately justify to their superiors as cost-effective. That much time spent on GLs they obviously can.
Having said all this, yes the game has made enough money and does on a regular basis to have a higher % poured back into the game, the dev team needs more help or better management or something because the rate at which they get things done and the quality of the product delivered is not justifiable in itself.