We actually have clauses in our TOS that tell you flat out that there is no chance you're getting a refund ever for any reason and to make any purchases with that knowledge in mind lol Over the years, we've had our share of chargebacks. Thankfully, not that many considering how many transactions we've made.
We get 2 kinds of chargebacks, one of which we always win and the other we always lose. In the beginning, if a person was merely claiming they did not get the item they purchased, I would send them tons of documentation, such as screen shots of the panel that show the points being issued and of places in the game where the player spent those points.
After winning a couple of those, we randomly lost one. So I called and asked for an explanation of why that one was different. The woman looked over the details of the case and admitted that the chargeback should have been denied almost immediately. The biggest reason? PayPal does not give buyer protection to intangible goods. With the decision already being made and carried out, we didn't get that one back, but now we just call one of the reps on our case, explain the way it works (completely automated) and that they ALWAYS get them as soon as they pay, and they handle it from there, in our favor.
Now the ones that REALLY suck are when the person claims that someone else used their credit card or account to make the purchase and the chargeback is initiated by their bank. I have sent sooo much data, including messages and chat excerpts where the player has blatantly said that they were pissed and therefore going to go file for a chargeback, but because the bank makes the ultimate decision on who wins, obviously it usually falls to their customer. If I see that it's that type of chargeback, I don't even bother to dispute anymore. As was said before, I take some solace in at least knowing it can only happen once.
So I guess my advice would be to actually call PayPal and speak to someone about it, get all the details on the outcome, and let them tell you what caused them to find in the player's favor. I always get better responses via phone contact than e-mail.