As everyone is telling you, the credit gets added to and increases the residual rather than, as you (and everyone else) would think, subtracted from the selling price. The treatment doesn't change the lease cost since it just changes the order in which the credit is applied. It would be the same either way. However, adding the credit to the residual makes buying the car at the end of the lease much less attractive since the buy out price will be high.
In your example, the car would be $35K. If the residual starts at 50%, then that's $17.5 (FYI I don't know what the residual is, I'm just guessing). The $7500 tax credit gets added to that, making the residual $25K. The adjusted cap cost is the $35K minus the $5K mark downs, giving a net buying price of $30K. So the depreciation for the lease period would be $30K - $25K = $5K, and the depreciation would be $5K/36 months = $138.88. That won't be the lease price because you have interest both on the depreciation and the part of the car you're not buying as well as various other fees, but that's basically it.
At $22K the Volt is the best buy for a car on the planet. Even with the way the residual is treated, it's a very good deal on the lease well but going in you need to know you won't want to keep it.
In your example, the car would be $35K. If the residual starts at 50%, then that's $17.5 (FYI I don't know what the residual is, I'm just guessing). The $7500 tax credit gets added to that, making the residual $25K. The adjusted cap cost is the $35K minus the $5K mark downs, giving a net buying price of $30K. So the depreciation for the lease period would be $30K - $25K = $5K, and the depreciation would be $5K/36 months = $138.88. That won't be the lease price because you have interest both on the depreciation and the part of the car you're not buying as well as various other fees, but that's basically it.
At $22K the Volt is the best buy for a car on the planet. Even with the way the residual is treated, it's a very good deal on the lease well but going in you need to know you won't want to keep it.