It sucks you got ripped, but jesus, you only have yourself to blame.
http://pages.ebay.com/help/policies/...ts-policy.html
Not permitted on eBay.com: Sellers may not solicit buyers to mail cash. Sellers may not ask buyers to send cash through instant cash transfer services (non-bank, point-to-point cash transfers) such as Western Union or Moneygram
They can't make it any more clear than that..