After some further investigation, I discovered that my calculation exactly matches the upper bound stated by the National Renewable Energy Lab's estimates on co

After some further investigation, I discovered that my calculation exactly matches the upper bound stated by the National Renewable Energy Lab's estimates on cost, "$200/kWh" http://www.nrel.gov/docs/fy02osti/31689.pdf http://www.nrel.gov/docs/fy02osti/31689.pdf But yes it looks like you can also manage about half that cost for a similar system (their stated range is $80-$200 per kWh).