I see that most people are scammed in paypal deals but also in bitcoin but less. I consider bitcoin better than paypal in some cases and paypal better in some other cases(for fast deal and buyer protection)
paypal is good with refund system for buyer protection, but this system is bad for seller
sometimes buyer receive his digital good and try to refund his paypal transaction
But if you have proof that you have sold something and it has been delivered to the buyer they can not refund you.
That's not 100% sure, but most likely. I had a situation when I have bought a cheap but very good looking phone on ebay with decent specs. Next day the feedback started to show up that the seller is a scammer. The seller has not sent anything after the payment, so I have opened a dispute in Paypal. After the dispute, the seller have provided a tracking nr. which was legit. Dispute has been waiting for the tracking nr. to show if it will be delivered to me or not. A bit later the post delivered me a small envelope, I have signed that I have received it. The seller has sent me an empty(!) envelope just because of the tracking nr. to Paypal. That moment I thought that I have lost my money, my luck was that if I order something above $10 I always do a package opening video. With this and with a lot of phone calls to paypal and much more email conversations, I have managed to get my money back, despite of the proof of delivery, but it was a long fight and a lot of hassle...
Sending a blank envelope with tracking to deceive ebay and paypal? That is a new low.