This article echoes my own experience recently with photovoltaic cell prices:
In April 2010, a PV system cost $8 a watt.
Now for 2011: the latest prices we've been getting for PV are $4,500 per kW before tax credits. It's dropped 45% since last year.
I had an eerily similar experience. I made a preliminary budget for our zero energy home solar array and assumed $7 a watt. But then I spoke to a local solar contractor we work with about this pie-in-the-sky pet project of mine and he had to laugh when I told him how much I'd estimated. He explained to me that huge increases in production capacity solely in the last few months have dropped the price dramatically, down to $4.50 a watt.
If it stays this way, the implications of this are fairly important. The link author says it better than I could:
It means we're not far off from PV being the cheapest source of electricity you can buy everywhere in the whole country, even in the parts of the country with access to cheap and toxic coal electricity. Is that time five years away? Ten years away? It doesn't really matter; either one is a very short length of time, and we should get ready for that and pay attention.