is there a blue book" for toy hauler brands

First off I'm assuming you are taking used. The problem with NADA is it estimates based on sales, so it can vary wildly. But gives you some idea. Though many times private sellers don't care about what you've found, they are selling it based on what they owe. Going to www.pplmotorhomes.com is a good source for any RV they are a large volume dealer, a lot of consignments and trade-in's that tend to move fast. Spending sometime shopping on the various RV sites will give you an idea of what things are going or and what's not moving fast.