Think of it this way then. Thats 50 million spent, which they either:
A. Got paid back if the figure was not met (means they made NOTHING)
B. Got paid back the 50million + other royalties from higher sales
C. Lost if the 50million number was not met (if it wasnt a "loan")
Either way, MS could not have made very much off of this deal. Sony on the other hand, kept the franchise + a new IP + its royalty sales for nothing. From a monetary standpoint on the game itself + dlc, Sony came out the winner. From a brand standpoint, MS is the winner due to the game now being multiplat from now on (I assume). Basically, short term Sony wins the monetary battle, but long term MS wins since the next installment will not require MS to pay a dime.