I recently did a pretty serious study on the cost of car ownership. Of course the big costs are the cost of money (no matter how you pay for it) and the cost for depreciation.
The cost of maintenance was pretty insignificant. For example, if you followed Lexus LS-430 maintenance recommendations to the letter, you are only talking about 4% of the total cost for 100K miles over a 10 year period.
In order to keep the cost of ownership as low as possible you need to do one of two things.
1) For short term ownership such as with a lease, buy a car with the best resale value.
2) If you really want to keep costs down, buy the most reliable cars, invest in good maintenance and run them into the ground.
The more frequently you switch cars, the more money you are going to spend.