There are several leasing guides you can find online that explain the money factor, residual value and capitalized costs as well as fees and how they intereact to come to a payment. Cars that have high residual values have lower payments so while it seems counterintuitive a higher end car with good residual values can cost less than a lower end car. For example we leased 15 cars for work and when we did our research leasing the base model which was cheaper to buy was actually more expensive to lease because the residual values on the higher equipped models was several percent higher. I point that out because you won't find that tid bit in any leasing guide.
The best way to get a good deal on a lease is have tier 1 credit, those who are lower tiers pay higher money factors (interest) and look for a factory advertised lease special. Those factory sponsored deals will be the best you can get. You should search for the money factor and residuals for the car your interested in before you go to the dealer. FInd a Mercedes message board and someone will have a post with up to date information. Both residuals and money factors change from month to month, residuals are the most volitile. If you spend 99 cents you can get a lease calculator for your smart phone, so when your at the dealership you can plug the numbers in and see what the payment will be.
Finally a lot of dealers will try and tell you that they don't negotiate the price on cars that are being leased. That is BS they use to try and rip people off. Remember when your leaseing your paying the difference between the sales price and residual plus interest in your payments so the higher that sales price the higher your payment.
Do your research and be prepared and you can make a lease work for you.
