Double check your model number. With the 2007 model year of Cougar fifth wheels, the only model with "RKS" is [243 RKS].
We were also unable to find a model with 278.
Alternative directions for a [2007 Keystone Cougar 243 RKS] follow.
When your RV is in exceptional condition or has any additional options, it is best first
to consider the base value of your fifth wheel and then make adjustments for new tires, batteries, etc.
Below we have provided directions to find the blue book value using a base price from NADA Guides.
You can follow these steps and adjust pricing as appropriate. Also consider contacting your Keystone RV dealer to consult with them regarding the value, plus other websites such as RV Trader which have comparable sales for popular models such as yours.
Select = [RVs]
Type = [Travel Trailers / 5th Wheels]
Manufacturer = [Keystone RV]
Year = 
Model = [Cougar Series / 243 RKS]
Options = [Select]
[Get Base Pricing]
Suggested List Price = $26262
Low Retail = $7350
High Retail = $8850