Envato aka Themeforest allows theme designers and developers to sell their themes for a percentage. There is no try before you buy so if you buy a theme that has sold 48k times and expect it to be good, and it turns out it isn't that great and even though it says it has features you want they aren't exactly what you want and don't work how you want them to work- their refund policy is denied. However, If you leave a review of your purchase that is negative, they will refund your money which means your negative review is removed and thus protecting their theme resellers from that review affecting their sales. Pretty dishonest.