You could look at their earnings reports. EA's profit margins are about the same as they were back in PS2 years, but if you took MTX out of the equation their profit margins would be a fraction of what they were in the PS2 years.
There's also just obvious common sense. US price changes below:
Game price increases since 2006: 0%
Inflation since 2006: 27%
Movie ticket price increases since 2006: 42%
Disney theme park tickets price increases since 2006: 77%
It's obvious game production costs have soared. It's obvious prices to consumers haven't seen the price rises typical with other entertainment. Something has to fill that gap. Again, this is easily seen by viewing the earnings reports which are public.
An AAA game changing its business model rather than changing its price with inflation is a choice, and imo a really stupid one. Turok: Dinosaur hunter for N64 was $80 in 1997 when the standard was $50. Goldeneye was up there too. Going above industry standards in price for a cutting edge experience is not some game changing concept. If a game is good enough to have a huge budget, charge for that budget. If the game isn't, then the its AAA budget is unsustainable. Hiding initial budgetary costs in post-sale transactions is a dangerous path for the industry long term.