I know Sony is guilty of throwing MTX into their games too, such as one of their racing games, and TLoU remastered. But the vast majority of Sony games have been completely free of MTX. I expect Halo Infinite to be a full $70 and have MTX in it to boot. It'll probably be the last new Halo game, and 343 will probably just keep adding on new DLC content to it forever. Kind of like how Destiny 1 and 2 got a billion expansions that made the initial game obsolete.
I believe the multiplayer is free to play. Of course there will be MTX, it will be like COD:Warzone.