The game will cost $10 per month to play (much like other online games), and you'll naturally have to factor in the costs of both the indoor bike and sensors if you don't have them already. Right now, though, the real catch is simply getting to play. Zwift just launched its beta test with a mere 1,000 open slots, and you'll have to wait until the winter if you don't request an invitation in time. Having said this, it might be worth the wait if you've ever wanted to compete against other cyclists all year round.