The higher the turbine is off the ground, the higher the wind speed will be. The most important task is to get above the initial ground turbulence. After the first 80 feet the wind speed gain is a little less but still constant. Residential scale turbines are usually on towers about 80-100 feet tall. Utility scale turbines are usually on towers from 130 to 230 feet tall.
Smaller turbines tend to be twice as expensive per kilowatt.
The price of smaller turbines is falling as the demand for them increases. There will be additional cost to interconnect this turbine to utility transmission lines and transmit the power. These are average costs as of this writing. In a wind farm, the output from all the turbines is collected by underground cable to a substation. At the substation the voltage is transformed to match the line voltage of the transmission line.