How does leasing save you from depreciation? Surely the company leasing you the car has a good idea of what the depreciation will be, and they want to make money.
Some of the manufacturers put a high residual on the lease because it moves vehicles. They'll presumably be losing money on the deal, eventually. But the nice thing about leasing is that you decide in advance what the depreciation is going to be, so you get to make it a certainty and base your decision on that.