Wind turbines are pretty expensive from what I've seen. The cheapest Bergey is a 1kW model for around $6,000 before install. Prices go up from there for the better systems. My guess would be that the "break even" point would be several years out depending on wind and maintenance.

Mariah Power has come out with a new system according to NPR. It's cyndrical in shape instead of blades at the top of a tower. It's cost will be @ $5,000 but is still in the testing stage and dosen't come with the batteries that the Bergey does.

If you have the upfront capital, then a turbine might be an option.