On the 1999 Ultra Masterpice's, I'm glad to see they are graded by PSA and not Beckett. PSA usually does not grade sheet cut cards, where Beckett will grade anything. I feel better that my Mariano is at least a real card.
On the Pinnacle bankruptcy cards, there's no Mo so I'm not obsessively researching this but I will say that PWCC does make a decent effort to police their listings. They pulled a fake Mariano auto when I pointed it out to them. The consignor sent it with a PSA sticker and cert but they took my word for it knowing my Mo collection. They will also ban a bidder forever if they are caught shilling. For guys with high feedback like that, I'm assuming they're either serious collectors or flippers and getting banned by THE biggest ebay seller out there would hurt. I'm sure some shilling gets missed, but I would bet that they are watching those listings closely. If you see something truly suspicious point it out to them, they will respond.
I've read dozens of threads talking about why PWCC gets higher prices for their listings than others and I can tell you as someone that buys some decent high end stuff, that they simply have the goods. Not just the good cards, but the best examples of the good cards. I wanted a 1975 George Brett in a PSA 9, and not just any 9, but a perfectly centered one. Guess where I bought it...
I spent a good chunk of my downtime the last 3 days just looking through their new listings. One nice cards leads me to another which leads me to another, and so on. I think I have 50 cards of theirs on my watch list. It's so easy to get caught up bidding before doing some research to make sure you're not paying too much.