How do you know that 500 people didn't buy a scam product this month? I put as much faith in the X people bought this as I do the X people have this in their cart. It's all a way of trying to stoke FOMO
You don’t. However, that risk is mitigated with a simple, easy to use return policy, where you actually get your cash back (not airline vouchers or points or made-up things to keep you in the ecosystem).