http://solarhbj.com/news/in-los-angeles-incentive-debate-heats-up-as-pv-price-plummets-01011

And an interesting comparison of the falling cost differential between residential and large scale PV installations.

http://www.renewableenergyworld.com/rea/blog/post/2010/11/distributed-small-scale-solar-competes-with-large-scale-pv

Looking at your table with that price as opposed to $7/W –

Total price of 4k system $16,880
Utility company rebate (7,800)
State rebate (1,000)
FTC 30% after state rebate (4764)
Net out of pocket 3,316

Payback 2.9 years (effectively a 24.8% rate of return on investment).

Of course as system prices drop subsidies are almost certainly likely to track them downward. The subsidies will have been successful in creating a sufficient market to create innovation and economies of scale.)