The interesting thing in this post for me is a link to an Earth Policy Institute page which shows an exponential decline in photovoltaic prices over the last 33 years, from $100 per watt in 1975 to $4 a watt today.
That's a highly encouraging long term trend. It reflects a "cut the price in half" time of about 5 years, which bodes very well in the long term.
Lots more stats available at the Earth Policy Institute Solar Power Indicators page.
mez