It's a valid question when you look at the numbers, but it's definitely not a Ponzi scheme. If players aren't pros and don't practice proper bankroll management. Even if they give you a $66 ticket, most recreational players will burn through it quickly. Second, nobody is guaranteed to cash (ITM). Those staked tickets mean ACR only pays if you win, and even then, they keep a massive chunk of your action while getting a active player in their field.
Lastly, that money rarely leaves the site. Players who win those tickets usually recycle the cash back into cash games or other tournaments, where ACR keeps collecting rake. It's just a customer acquisition cost for them.
