You buy the game Sims3 for $50.00. You don't pay x amount of money to play it each month. You also can't play it online, but you can upload things you've customized in the game to this website and talk to other players, on this website. The game itself, is offline.
Comments
You are approaching from the wrong angle - this is an offline game with online 'features'
1) Umm... 1 hundred billion? (J/k - no limit)
2) About 50,000 Simoleans... in other words, 0.00 real world money
Hope this helps.