You are right. Any collectible value guide book starts getting old the day it is published. But the values in relationship to each other generally stay accurate.
If a certain gas pump has a value listed at twice that of another model pump, even if the dollar amount changes, the value difference remains. So if you see the more common pump going for a certain price, then the more sought after model's value is higher by the same proportion as in the book, if not more.
Also condition and location are major factors. If certain parts are missing, it can seriously hurt a pump's value. If it is located far from a potential buyer, transportation is a major consideration.
So don't think any guide book or auction price is always accurate for your similar item, now or forever. But if you see a Wayne 60 for the same price as a Bowser 585, go for the Wayne. (Sorry Bowser guys, no offense intended)
------------------
Oldgas
Your host and moderator