I'd guessed about £300 for that Zaskar so i agree 
with the previous $400 - $500 estimate, it does look very nice  
 
 
£50 plus post (ten quid ?) seems reasonable for the P3 frame, i'd 
give 
it a clean first though 
 
 
The RTS, are you selling the whole bike or the frame ?, (i assume 
its just the frame as you dont mention any bits) there was a reconditioned RTS 2 frame for sale on here recently for £100 
(seemed like a very good deal though) so that could be a guide, 
about £250 for the whole bike depending on spec.
The LTS frame, the DH model is much rarer than the standard 
LTS, as mentioned that one sold on E-bay for £142 seems like a 
bargain though i think the shock and bearings needed serviced, 
i'd think £120 - £140 would be fair for a good std LTS frame, a 
bit more for the DH version.
A pic of the Klein would help, being a 96 Comp i'm pretty sure 
it'll be a post Trek frame, sounds like a very nice spec'd machine 
though, i'd guess at least £500 ? (what that'd be in $'s) maybe a bit more.