You can get lucky sometimes with your trade in value. I am getting my first BMW at the end of this week. I have a 2012 Hyundai Sonata Hybrid that I began leasing in May of 2012. The buyout, which includes all fees, is $22,500. My BMW dealer is giving me $22,500 as a trade-in credit and they will be sending a check in that amount to Hyundai to buy the car directly. So, I am getting a brand new car for no money out of pocket (just MSDs and title and tags).
I have done this same scenario for other cars in the past 2 years. This is my 4th leased car in 2 years and I have never put any money down and always get the dealer to completely pay off my current lease. I am doing the MSDs this time because I will keep this car for the 3 year term.