Current commercial-scale wind turbines cost in the neighborhood of a dollar per nameplate watt.  The foundations, installation, and grid interconnections are extra.

If sited well, the economic benefits are considerable.  Jerome Guillet of The Oil Drum has noted that wind displaces the most expensive generators on the grid at the time.  This lowers the market price of all the electricity on the grid, and can save consumers much more than the actual sales price of the wind power itself.

Wind farms can pay back their invested energy in as little as 3 months.