Reading from the Good News, Bad News Dept. ....
First off, the first half of the following article might be helpful: http://geniimagazine.com/forum/cgi-bin/ ... 578#000000
Bad news first: there is no single source to turn to when it comes to pricing magic books. Pricing magic books is a form of art. Its not always cut and dried, nor is it always dictated by the market. Price guides like Canicks and Cartlidges serve a valuable, albeit limited, purpose, but only for those people who understand the limitations and biases inherent in such guides. So do general bookseller sites on the internet. As you observed, prices are all over the map and relying on Addall, et al. as a pricing guide carries the same dangers as relying on Canicks guide the spectacled and/or blind leading the blind.
The good news: you clearly want to learn and you have an open mind. For pricing in the near term, your best bet is to make friends with an experienced dealer or collector and find some way to make it worth his while to help you. Many guys like Dick Hatch and Byron Walker will gladly help you with one-off pricing, but it gets burdensome if you toss a whole list at em and ask for pricing. Theres no easy way to learn this game. It takes time and you pay your dues or you just pay.