I honestly hope that an attempt to sell GTA 6 at $100 would blow up in Rockstar's face big-time and result in their stocks tanking. Not only are they trying to set a bad precedent, but GTA Online is heavily monetized. They have Shark Cards that cost $100. And unlike a lot of MTX-supported games, GTA Online has a heavy pay-to-win element to it. You can grind like hell to try to get everything in it, but you're going to be at a disadvantage to the whales. There's even a Shark Card called a "Whale Shark Card," and it isn't even the biggest one they offer.
But, they will get away with it. They've perfected digital heroin and their customers are hooked. Other studios might get punished for $100 games, but Rockstar won't. They're a meta example of the greed they parody in the games.