Made the mistake of taking one home for the evening - 535 M-sport with HUD & Nav, CPO. They're asking $35k, which seems to be quite a reasonable starting point. Absolutely love the car.
They showed me the BMW internal maintenance documents, however. HPFP replaced at 9,330 miles, first documented oil change at 22,999 miles. Not a big fan of that, for sure. Next oil change right before it was turned into a CPO at 41,000 miles. It is for this reason that I see V8power's point. I guess I should walk away and find one with documented oil changes at closer intervals.
PS: They had an '06, 108k mile M5 that was in great shape. Tooled around in it for over an hour and was blown away by how solid it felt. All maintenance had been kept up on it, but it had right rear damage history that was invisible as far as I could tell (the repairs, that is). They were asking $24k. Only for a few moments did I consider socking away $7,500 for future repairs/maintenance and driving off in it. The car does NOT need a radio - just press the pedal on the right...