The going price for a basic mechanically sound M-35 6 x6 deuce and a half is still about $6500 to $7k.
With tank, pump etc. I'd wager the truck could bring about $8K.
Most M-35's that are acquired thru surplus property agencies have some reversionary requirements upon termination of use. Accordingly it is possible that open market sale might not even be possible on the RGRPC truck.
I agree that the truck belongs with the C & T SRR.
They do not need a NFPA 1901 compliant pumper. During drought operations the railroad made great use of the truck by escorting the trains up the hill, then dumping the water into the Cresco tank on the journey home.
I just think that the truck would run better with something other than the yellow paint on the wheels!