Ok, things make sense now. Last night when I built and saved 335i sedan the final price was $50,345. Today it is still showing $50,345 in the list of saved cars. When I retrieve that saved 335i sedan today it shows a price of $48,895. The difference is $1,450 which happens to be the price of the leather seats. There must've been a bug in the web site last night that charged me $1,450 even though I had the premium package selected.

With all that said, the leasing costs still seem backwards. A 335i sedan costing $48,895 with $4,000 down and 36 months/12,000 miles costs $647 a month. A 335 coupe costing $49,695 with $4,000 down and 36 month/12,000 costs $642 a month.