I just sold a lens on eBay and got into an unsolvable problem with a potential buyer from Norway.
He wanted to pay through PayPal, so he would have had all the buyer's protections but he also wanted me to ship it with a receipt for $100 instead of the $1,000 price.
I made a few calls. The Post Office representative said they would sell me the insurance but that I would have a hard time proving that the lost $100-valued lens was actually worth $1,000. FedEx basically said the same thing; that buying insurance for a certain amount was not guarantee of that amount of reimbursement and that they would look at all documents.
Both of shippers and PayPal said that if the buyer doesn't receive the lens from customs, by paying duty on it, the lens would be sent back to me, doubling my $150 shipping cost. So, the buyer could have waited to see if he got away with paying less than full duty before deciding whether to accept the lens or not.
PayPal said that they would mediate any disputes but that the proof of delivery is on the seller, and that the seller also has the burden of proof for the delivered item being undamaged and as described.
PayPal said that shipping insurance would be the seller's only recourse and that PayPal never covers both the buyer's loss and the seller's loss.
I asked what would happen if the buyer claimed he received a brick in the package or what would happen if the buyer got a refund because of some problem with the lens, but instead of mailing back the lens he mailed me back a brick. PayPal said that I would have to prove the case to them.
So I asked if I'd be able to prove these things by showing a video of the package being boxed, labeled, and mailed. Or, conversely if I could prove my case with a video showing the unwrapping of a returned brick. At that point PayPal said that they would not look at those videos because they don't get involved in legal matters!
We couldn't come up with a way that I could ship the lens to the Norwegian buyer with a reliable insured value so I sold the lens to the second highest bidder for $5 less.
My conclusion is that, even with PayPal watching over things, there is still a lot of trust and a lot of CYA involved in every deal.