Kelley Blue Book does not provide values for RVs. NADA Guides does provide blue book values for your travel trailer. But, those prices are for low and average retail.
You can contact a Keystone dealer to find out trade in value.
Steps to find a base used value, including adding options and location, follow:
Go to [www.nadaguides.com]
Select = [RVS]
Select = [Travel Trailers / 5th Wheels]
Select Manufacturer = [Keystone RV]
Select Year = 
Select Model = [26 RBPR / Bullet Premier Ultra Series]
Enter Zip Code = 
Options = [Select]
[Get Base Pricing]
Suggested list price = $34338
Low retail = $17350
Average retail = $20900