Even though costs of AAA games have gone up for some games (certainly not all) because of the size of teams/labor hours, so have the volume of sales. Publishers have made more and more profit while the average price of AAA games had stayed about the same for a long time.

Games selling in the hundreds of thousands was considered really good decades ago but now those are in the tens of millions.

Publishers aren't having problems with profitability, so much so that they've been buying up large swaths of development houses and IPs and then dismantling them when they have a single flop.

EA's gross profit in 2010 was $1.6B, in 2014 was $3.03B and in the past 12 months have been $5.8B right now according to macrotrends.

But the current trends are unsustainable

The current trend in profitability is increasing, not decreasing. It isn't a minor trend or minor increases either.

Major publisher profitability has vastly increased in spite of stagnant game prices. They don't have to increase prices to increase growth. It is simply that the market allows the increase of the price with more profitability and so they do.