Classic scam, I forget the details but the buyer overpays, you send the goods and the excess payment back. The whole lot turns out to be fraudulent and you end having the original payment rescinded. You are therefore out of pocket due to sending the goods and some of your money and receiving nothing in return.
I forget the intricacies but they tempt people by appealing to the greedier side of human nature.
Take a step back why would somebody offer far more than the current price? If you need to think about that you should question whther you should be using e-bay at all.