I never understood the idea of selling in-game currency in a game with such terribly weak book-keeping. It happens in MMO style games because someone is keeping their finger on the economy. Rockstar never once treated GTA Online that way.
There was a time (maybe still, I don't play the game) where cheats would cycle through every existing lobby and spawn millions of dollars into the inventory (or on top of physically) every character in the lobby.
Now I see that Rockstar is slowly pivoting from the cash sales into car sales -- gee, wonder why. Spawning cars is less common but still fairly easy; one imagines this is coordinate with work that would make spawning cars less easy -- but maybe that's too charitable here.
Sucks for the players that haven't cheated their way into owning EVERYTHING (which has been trivial for years and years just by being the random recipient of hacker money), and yet another boon for the cheaters who now find themselves with even more exclusive treasure.