The UK governments starting FiT rates were too high to sustain. In hindsight it should have been started around 25p/kWhr. Now this reduction of FiT will dent the confidence of the industry. 43p/kWhr was too and also attracted a lot of opportunistic companies not necessarily because of the success of the technology.
Why we talk about the pay back period all the time? PV and the green technology is some times a life style choice. PV is going to reach grid parity in the next year or so. Some utility level companies (two I know about), who are producing CPV are already the lowest in the industry for plants > 1MW.