Rarity becomes irrelevant when there is a steady, ample supply of something and a tiny, shrinking demand for it. They will depreciate down to under $10 grand in a very short time, IMO, as cost of ownership goes postal w/ fuel and maintenance+ insurance.
Those cars were the shizzle when they came out 8 years ago, but there was never a big market for them and they are now quite dated compared to the latest M-series offerings. For better or worse, M5s are status cars and the market is for new ones.
I would guess that a person could lease a new 335, (which I would much rather drive), for less than owning an old M5 if both were used as DDs. I know that you are not using it as a DD, but put yourself in the buyer's shoes, resale-wise. They are a maintenance $$ sinkhole, (brakes/tires/electronics/etc.), and new BMWs are 100% maintenance-free down to brake pads for 4 years.
I personally love the M5 that was immediately prior to this one, (mid-'90s), but apparently they were not great cars and also $$ pits. The real fuel efficiency of these cars is ******* awful if you use your right foot at all, (and otherwise what is the point), my buddy had a new M5 in 2000 and complained about MPG then. And he was making $500k a year and premium was ~$1.60 @ gallon. Stuff to ponder...
