The only way to be 100% sure with paypal is to do the deal like it's a material good.
The buyer wants 50k gold? Fine, they get a printed screenshot. A photo of the 50k gold

And the gold of course. But you make it seem like you charge them for the photo. You go out and send the package with the photo to them (adding the postage to the price). You keep record of everything you do, tracking numbers etc.
So if they want to charge-back later they have to prove you didn't send them anything. Which is hard, cause you have photos of everything including the package tracking # with their address on it. Try to scam NOW, bitches.