Agree as a collector that trades are hard as recent win cost have gone higher but "Book" value to me is more for insurance use as I have never really tried to sell for profit over face of more than a buck or two to cover hold cost for the early releases that help new collectors catch up.
ALTHO - would be great to sell a 93 Riviera for $16 so I could buy a new release or even for $40 to get a real short run to fill a hole - like sex sometimes you wait for the urge to match. lol