So... that means that the either:
1) The provision in the contract can't mean "we have the write to breach whenever we feel like it"
2) or, that the TOS are unenforceable.
The wording in the TOS is designed specifically to not mean "we can breach whenever we want", but instead to mean "if you sell counterfeit goods through our service we will destroy them and not refund your money".
The words "we ... reasonably believe the item you sold is counterfeit" were deliberately chosen for this purpose. The fact that paypal can use its sole discretion just tips the scales in their favor. If they have reasonable evidence that something is fake, then they can destroy it, even if they haven't done due diligence to prove it's a fake.
The question comes down to wether or not paypal had reason to believe the item was counterfeit.
Their are certain cases where only a customer complaint would be sufficient to establish a "reasonable believe".
For example, if Picasso bought a painting that was said to be a Picasso original, and he called paypal and said "I didn't paint this, it's a fake", they would definetly be within their rights if they distroyed it, even if further investigation could have revealed he was lying.
In this particular case... you could potentially argue that the customer's complaint was in no way sufficient for paypal to reach a "reasonable believe". This does make the whole thing wildly open to judicial interpretation, however.
Its a shame that contracts have these kinds of protections in them that most people are unaware of as they get pummelled by these sorts of contracts.
Principle. (JSYK)
In any case, once someone posts a comment I can't edit a post, so by posting a reply about a typeo, you only ensure that it will never be fixed....
tl;dr lawyer up.
They had a professional appraisal on the violin that said it was authentic. Paypal has its TOS saying they can call anything counterfeit and their TOS says they can't be held liable for it.
Sorry it's a judges job to say if you can or can't be held liable for your business terms and practices.
(Americans also make typos which look odd to Britons, for example "mute point".)
So there's that.
I think that tossing a coin and using reason are different, and I believe that a court would uphold my expectation that reason was used. Paypal will then have an opportunity to present their reasons. In this case, IMHO, it would appear that a "reasonable standard" of "reason" was not used.