sabashiokaki - You say it is a given, etc. but that is not true. Right after you posted that, ravetek posted he's bought cars sight unseen. I know several people who have purchased high-dollar used cars sight unseen and never had it inspected by themselves or a third party. Some of them have gotten really burned. You may say they are idiots, but that doesn't change the fact that people do it.
ravetek is right that unless you have the option to pass on the sale if you find problems upon inspection, you should not proceed. But few of the NSXs for sale on eBay offer that - most want at least a nonrefundable deposit right away. So by setting up a sales deal skewed totally towards the seller, the average bid amounts will be lower than "fair market value" because many real potential buyers will be scared off of those cars.
And, if they do have it inspected and find problems before the auction ends, the buyer and seller may agree to a lower price than it would otherwise go for. Then the buyer may place a bid in the agreed amount and the seller then either ends the auction early at that price or cancells the auction with them as the high bidder. So once again the price you see on eBay does not reflect real-world pricing for a "clean" car.
The same goes for regular car auctions. Cars are a commodity at those auctions and volume buyers know that X percent of them will need Y dollars on average to be in "top" shape. That's why cars at auction are cheaper than other places. On average it will work out, but if you only buy a few cars that way (through a friend, etc.) then you have the chance to get really lucky by getting a mint car that needs nothing, but you also run the risk of getting burned by one that is a basket case.
And yes, there are PLENTY of '97+ NSXs that have serious problems on the used car market.