$100 is a fair asking price for a AAA game of this size and scope. Not all games should cost the same.
People forget that almost all new games cost $60 in the 90s and a lot of them weren't even that good. $60 in 1992 is over $130 today. We're downright lucky that most new releases still cost the same and have resisted the effects of inflation.
Sure, wait for a sale if you don't want to pay $100 on day one. But don't go thinking $100 is some outrageous cash grab. The game cost over a billion dollars to develop and will likely give you hundreds of hours of entertainment.
In the 90's, a game was also sold as a finished product, and even an absolute blockbuster was lucky to sell over 100,000 copies. GTA V and its seemingly evergreen online playground have sold countless millions, and GTA Online has made them an honestly disgusting amount of money.
It was their decision to spend such a ridiculous amount on GTA VI's development, and they will likely still make it back ten+ times over over its operational lifetime, even if they sold it for $40 or less. Only a fraction of GTA V's revenue came from full-price purchases after all.
This is just them trying to take advantage of the fact that the average individual has no real clue how the economics of a game like GTA V actually work in order to justify a move that would be done out of pure greed.