Sure, I'll jump in.
Time for a cop-out answer: Mike Richards, the host of GSN's Pyramid and Divided. He only left the show a year ago, so I'd assume he still has some rudimentary knowledge of the prices and have the best chance of winning. He undoubtedly would have access to how they price the trips, which is perhaps the hardest part to price, and prizes like the E16 and Vespas don't fluctuate that much between seasons.
Now, if he can't because of legal issues, David Ruprecht from Supermarket Sweep would probably do the best on the grocery products, although he wouldn't know much about pricing things over $25 besides cash.