Opportunity cost is not about the amount of money you spend, it's about what you spend it on and the returns you make on your investments. You can spend the same amount of money, but receive bigger or smaller returns depending on the choices you make. Sony does not have an endless supply of money to make investments with, so the returns they make based on their choices is important.Is it really a question?
The answer is yes. The answer is no.
The could spend less and make less. The could spend more and make more. The could do any permutation of the two.
Sony's strategy seems to be to have a large first party developer network, which costs them a lot of money. But the resulting games are met with mixed consumer reception, even though some are critically acclaimed (e.g. Uncharted, KZ2, LBP, Lair etc). MS's strategy seems to be to rely much less on first party developers (Bungie and Ensemble are both let go, even though their titles are top-notch), but to cherry pick their titles from thirdparty developers. To me it seems their investments have seen much better returns (e.g. Gears, Mass Effect, PGR3).