Neither Kelly Blue Book, also known as KBB, nor NADA provide a price guide for trailers; TruckBlueBook.com does sell a guide for commercial trailers, as of 2015. While there is no definitive guide on the price of used recreational trailers, one can easily discover the value of a used trailer by looking at the prices of sold listings on websites, such as eBay.com, or by calling local RV dealers and their websites.
Locating a "Blue Book" value refers to using a Kelly Blue Book, which is a specific guide published annually that lists the prices for new and used vehicles with different options and levels of condition. Kelly Blue Book does not offer a product or guide that describes the value of trailers. There are guides to help find the value for commercial trailers; however, unlike Kelly Blue Book or similar services, guides for commercial trailer values generally cost several hundred dollars.
The simplest way to determine the market value of a trailer is to research what comparable trailers have sold for in the area and how much other sellers are listing comparable trailers. Recommended websites to check the prices of recent sales and for sale listings include eBay.com, Craigslist.org and a local newspaper's online classified ads.