It's going to get more crazy, the more money in the game the more clubs will spend. It's not exactly shocking really, when you look at percentage of income then the Pogba deal is exactly the same as when Man Utd signed Ferdinand. Difference is their income is much, much higher so they can spend that easily.
Not sure why anyone think it's going to slow down, the money increases because the demand is there and the demand isn't going to slow down. There will be more fans and more fans equals higher sponsorship and TV deals which equals higher income for the clubs.