A couple of points. I'm not sure what you're referring to about the cost of making a Volt exceeding its MSRP. Do you have a cite for this? It's likely not true in the sense that most people would think of it. Most people think in terms of factory variable costs, the direct costs in labor and material. FVC very likely does not exceed MSRP. However, the fully loaded costs, meaning costs that include everything including marketing, R&D, and so forth, may very well may exceed MSRP. (The difference between direct costs and fully loaded costs is why Tesla loses money when its cars have a positive margin).
Then of course you have to add in $7K in ZEV credits and the contribution to CAFE. I suspect when you do that the Volt is profitable even on a fully loaded basis.
As for GM subsidizing leases, I think this is the wrong way to look at the issue. GM is discounting. The same discounts are available for leasing or buying. It's just that when leasing you get the benefit of the discount over three years rather than six or seven. In some ways the risk of a very low resale price gets shifted to the financing company. Since this is likely GM, you can say GM is subsidizing the lease, but not in a direct sense. On the flip side, if you lease you leave about half the tax credit on the table.