I'm not familiar enough with the pricing details to disagree with you, but it's worth mentioning that a Model S can be used for the UberLux service (~3x more expensive than UberX).
Uber pays over a dollar per mile for UberX. The GSA rate for autos now is $0.54/mile, which is intended to be an "all-in" figure for operating costs.
I think there's room for profiting from driving Uber. (I also agree that it's a good bit less than it appears based on the cash-in and cash-out every week.)