GunBroker places the Ruger Mk III's in the $250-469 range. Not many are threaded and about eight are fluted, but no premium seems to be being paid for either feature. It would seem that the your two Rugers are falling right into the mid-price range and are probably a good buy if in good condition.
“Malo periculosam, libertatem quam quietam servitutem." (I prefer the tumult of liberty to the quiet of servitude.). Thomas Jefferson
"All that is necessary for the triumph of evil is that good men do nothing."
-Edmund Burke, Loosely translated from Thoughts on the Cause of Present Discontents. (1770)