I don't think they are making money.
1. Invest to stock and gain 10%-20% in 3 months is not easy. Especial in this year, it's easy to loss 50% in 3 months.
2. Even if they make 10% from your money, they will pay shipping, cost of check (their check looks nice), salary for emplyee, 5% for ebates, bonus for CEO, blah, blah. 10% or 20% will not cover their cost.
The first time I order from them was more than year ago, when they opened their store on yahoo. They've been there for years, but, there are still people who never order anything from them. It's really simple to understand why they are still in buesness.