I see your point but if you want to go on that then you could move into a very small house in some dodgey area and save even more money - but in the end you're paying for enjoyment, comfort, and safety and I suppose that list could go on.
If you really like your MINI and you don't want the value to decrease at the rate that it will and you plan on keeping it quite a while then I don't think it's the worst idea.
The bonus is, if you drive a well below average car everyday, driving your MINI on the weekends will feel like absolute bliss. I went on holiday recently and hired an entry level car and when I came back and drove my
MCS I felt like I had died and gone to Heaven!