600MB isnt that much for 500 players! If ANY game here got even 20 players on playing 2 hours a day that would be a huge success.
Most game servers should be prepared to spend at least 20GB of bandwidth a month on it. Thats not much anyway.
I think that there obviously will be issues, but i dont think that the one you pointed out is really the biggest one. But yeah, you certainly have a point though.