Thats easy enough to say in auction formats or on these type sites but stores and most card shows need a guide BV to price by (even more so for comics). Consumers need to feel some sort of security that they are making a good purchase. frankly I don't belive in any of the guides for cards, comics or any other collectible. I agree that its only worth what someone is willing to pay and most times its no where near any of the book value prices.
In comics the Overstreet guide is a really consistent guide with market value. The biggest problem is that it is an annual guide and there are a ton of factors that can change the market value on a comic over a year period. A comic don't always keep the same value for 12 straight months. Wizard is a horrible guide. They are all over the board and I swear the set prices and promote comics by how much of a kick back they receive from the comic companies.
Overstreet is far more then a guide. I hardly ever look up prices as I have a pretty good idea on most all comic prices. I like reading it for ref material and for the write ups out there. Comics are a far different collectable then sports cards. There are so many different things involved from the writer, artist, colorist/inkers, letters, publishers, crossovers, 1st app, times (gold/bronze/silver/copper/modern, cross overs, guest app, deaths, variants (covers/price/prints) etc....Like I said Over street is more then a price guide its a valuable tool for any serious or beginning collector.
And to be honest the movies really only effect the lower grade or cheaper comics. People who jump on the character band wagons have no interest in spending huge amounts of money on a flavor of the week. The high grade spideys are always setting new record highs and the movies have no effect on there value. The true collectors are buying and selling because they follow the characters and the population on the grades of these comics.
The OverPriced Street Guide? Not my favourite. Neither is Wizard, for that matter.
In comics even more than in cards, it's only worth what someone's willing to pay. The Amazing Stories/First Spiderman might list really high, but until the movies came out you'd have a hard time getting that.