While I have respect for Jason as a collector, I hardly think he's a neutral party in the valuation issue. I see this same thing come up all the time on NeoGeo.com as there is one moderator who also generated the price guide that constantly prices his stuff above what most people agree the fair value to be and well above his own price guide. He always points to the alleged secret transactions of high value cart sales as his excuse for why his asking prices are so high. Simply put, someone with a vested interest in maintaining or increasing the value of something they buy and sell is not a reliable source.
I understand that personal transactions may occur and I certainly understand people wanting to remain private, but there is no reason that the price something is sold for should remain a secret. It's not like the name of the buyer has to be revealed. Frankly, as much as people complain about Ebay, it remains the appropriate means of determining the fair market value of items over time as it's a regulated public marketplace and there isn't a whole lot of room for slippy valuations and alleged transactions.
On your other point, equating games in the hundreds of dollars with games in the tens of thousands of dollars is ridiculous. Lots of collectors can afford spending a few hundred dollars on something and many do. With new games retailing at $60 nowadays and the MSRP on collector's editions going for hundreds in some cases, it just isn't much of a stretch. Paying $17K for something that is uncertain to be able to be resold for that much quickly is a whole different thing. I'm not saying it can't or hasn't happened, but it takes a very specific kind of buyer and a willing seller, neither of which are necessarily common. As such, items at the higher end are always much slower to appreciate in value and in every collectible market are the first to be hit when the economy goes bad. It's like any other asset that just isn't very liquid or capable of ready valuation. I realize you're a newer collector, but I have been through this cycle many, many times not only in video games, but in other collectibles like comics and coins. Just because a particular market is hot doesn't mean the most expensive or rarest items will share that heat, especially if there aren't a mass of rich collectors actively seeking those items out.