Only one group needs to do it for everyone to keep playing. Everyone running their own server isn't very interesting for multiplayer... Usually you'd do it in groups.
Most of the time, no group of players will run a server at that cost. So regular players still can't play.
It's not unheard of though. WoW and City of Heroes had/have large, expensive fan servers. But realistically, this legislation would save maybe 0-2% of games in the thousands-per-month cost range. According to the parent commenter, we might lose many more than that from the legislation causing studios to decide not to make them to begin with.