Budgets ballooned way out of the proportion of the consumer market growth, imagine your game got 10x more expensive in 20 years but the market only grew 2x, console market for example is basically stagnant in same hardware tier since 128-bit days.
Here's a food for tought: Bobby Kotick, regarded as one of the biggest assholes in the industry, is the same Bobby Kotick who greenlit games like Tony Hawk, Marvel games, Prototype, Soldier of Fortune and etc.. Because that's how you made money back then, however these franchises fell out of the market because of decline in quality and/or change in consumer taste (this can apply to Tony Hawk for example). Imagine that you could easily have ROIs at 300-500% on mid and high end projects, and now many studios have to settle for 100% at best, as this is expected to be Insomniac's case in their leaks.
Also this comes around the three issues
1) Forever games that didn't exist during the "golden years", are on top on the spending and these studios surely know how to maintain them at the helm.
2) Supply and Demand, too many good games for a slow growth public.
3) In case of the west: Mismanagement is at its peak with half of development time, and therefore money, being into waste.