All above is correct and well done. The only real item I can add to the lease vs buy decision is the implication of a large down payment if you buy. This could significantly reduce your overall cost to own over a 3 year (compared to lease) period or 5 year loan period. If you consider a $60,000 car with 50% down you could save as much as $4,000 to $7,000 by owning depending on whether you can sell it for the lease projected residual (62% on a 335i cabrio) or more.

I currently have a 2004 - m330ci cabrio with all the bells and whistles and the lease buyout is $31,000 and they are selling for $37,00 to $39,000 privately ($41,00 at my dealers !!). So I decided that I do not want to leave this on the table along with the finance delta and tax differential on the following vehicle (after my 335i).

My calculations show me saving about $6,500 over a 3 year period against an interest loss (after taxes) of just over $2,500. $4,000 in my pocket works for me !! I also hate paying the up front lease initiation fees and the higher lease interest that you seem to always get hit with. Sellijng a 335i in 3 years at 62% (or more) residual should be a no brainer - I'll take the risk. I also really want to customize this one and not have to worry about the lease and I really hate having to buy tires with only a year left on the lease - and you will with high performance run flats - guaranteed !!

These decisions are really very personal that's why there are so many choices !!