<< <i>it was a 62 mantle PRO 8.5 it already sold for $280 >> I'd say passing was the right move because if the card could have been in a PSA holder it probably would have been (seller has mainly PSA cards).
<< <i>it was a 62 mantle PRO 8.5 it already sold for $280 >> A 62 Mantle in a Pro holder at 8.5? I think you are probably better off not winning that auction. It is likely an altered card. Pro is more prone to miss things like tampering than the big 4.