You get $8300/month from renting spare rooms in your house? That has got to be a big house and you are a /very/ wealthy individual.

I bring this up because it seems like you ride Uber more for the convenience for your lifestyle and less for the cost factor. You could easily buy an old prius and not worry about most maintenance, deprecation, etc. Most ride shares I've been in have been a Prius or similar. As you said, "I've gotten very addicted to the pleasure of not driving the car that I'm riding in." You don't seem to value driving anywhere near being a passenger. Thus, selling the M3. <-- Not sure why you'd ever be buying an M3 if being driven around in a Prius at modest speeds was your thing. Was it just about the image?