You are going to need to show hard evidence to Paypal that this person scammed you, Paypal does not support virtual good trading so.. you odds aren't fantastic.. but there is still hope.
This has happened to me, hence why I only accept Direct PP from people who I really trust. Always use PlayerAuctions. That's a start
Ring paypal, explain the situation, ask them to check the i.p's from the time when the cash was sent, to the time the claim was made, if it was the same time, you've caught them.
I was charged back for 16.50 (nothing compared to this I know) but that fucked me over pretty good...I paid for a runescape membership after I got the money, which means that have negative balance...not I can't even renew my netflix unless this matter is resolved...