So is a prewar Kiev 2 or 3 the best of the lot, generally?
There are no "prewar" Kiev cameras.
You'd better read this first to know more about the Kievs :
http://www3.telus.net/public/rpnchbck/zconrfKiev.htm
Otherwise, I would tell that being asked to pay $500 for a Contax II is a plain rip-off.
A very clean Contax II with snapped shutter ribbons can be bought for less $100 at auction.
Once cleaned, optically/mechanically serviced and fitted with new shutter ribbons it can sell for $200-$250, max.
Any professional camera repair shop who can service a Contax II can service a Kiev the very same way, so I don't get that thing about professional camera repairers not wanting to service the Kiev cameras while they service the Contax.
Eddie Smolov or Steve Serota would service a Kiev with no problem.
Then you can find people who know how to service a postwar Contax IIa or IIIa camera and who don't know how to replace the shutter tapes of the Contax II/III and Kiev cameras, but that's another problem.
The advantage of the Kiev is that the lenses are obviously cheaper and whereas the J3 (50/1.5) and the J9 (85/2) can be used with the Contax, the J12 (35/2.8) cannot as the rear element interferes with the shutter.
This will get "mabelsound" confused. The Jupiter-12 35/2.8 lens fits the Contax II and III cameras and doesn't fit the IIa and IIIa cameras.
A quick abstract :
1935-1944 : Contax II and III, produced at Dresden, Germany
1946-1947 : Contax II produced at Saalfeld near Jena, Germany USSR occupied zone, as a training for the Volga project workers
1949-1982 : Kiev II, III, 2a, 3a, 4, 4a, 4M, 4aM produced at Zavod Arsenal, Ukraine
1950-1961: Contax IIa / IIIa produced at Stuttgart, Western-Germany (German Federal Republic).