.58 & .85 not so much - I bought a perfectly good s/h .85 VF M6TTL a while back for a very reasonable price. It probably depends on the demand for that VF type at the time.
Titanium bodies and other special editions - I don't know. One thing you ought to realise about all the special editions is that the collector's market (which is where the highest resale values will be found) require the camera (and lens where appropriate) to be 'as new'. If there are signs of use - basically, if the camera has been used at all (except in the lightest possible fashion e.g. a single film put through it very very carefully, the strap *not* attached, etc, etc) then much if not all of the premium vanishes. You're then left with with the 'Leica users' market, and they (by definition) are looking for good condition cameras at keen prices, to use. A user-buyer isn't very likely to buy a titanium M7 for twice the rate of a good-condition standard M7. In use there's no difference between a special edition and the equivalent standard model.
