Not sure if you are a BMW noob, but you must also consider the cost to maintain factor. If you plan on holding on to a car past 50K then you should familiarize yourself with the expected maint costs.
M are often time prohibitively expensive to perform maintenance on. Often time 30 to 50% more for the same service as a non-m car. Add to that the M mark-up on top of the BMW mark up on aftermarket parts prices.
Gas prices are also a consideration, they wont get any cheaper. Insurance is higher also.
That said, owning an M should not be about being "money wise". It's about being a connoisseur of fine cars. The M is a work of art. How do you put a price on that?
In any case, owning a car is much more then the sticker price.
- 08 135i - Wavetrac LSD, M3 front sway, Meyle HD links, Whiteline subframe bushings, M3 rear guide and upper link, M3 front control arms, HP custom M3 front Strut brace, Megan rear control arms, F30 brake shields -