Well, to be fair, in this instance these are not ASICs requiring special chip fabrication processes and capable of minings super-efficiently, which leads to manufacturers 'testing' them for extended periods when they are ready for shipping.
It appears these are a bunch of GPUs slotted in to a ready-to-run motherboard config, which means the only obstacle is ensuring that the OP isn't simply a blatant scammer who isn't going to deliver at all. Shipping a complete unit to a trusted member so they can verify the device runs as well as they claim should negate most people's concerns here.
As for paypal being an issue, they could actually avoid that problem simply by being willing to take escrow btc payments which are released when the buyer receives the goods and all is in order. Unless they are a two-man outfit desperate for funds they should be able to defer receiving the bitcoin until their customer is happy with what they've sent them and an escrowed payment would mean both sides should feel secure enough in the transaction.