The studies on the increased drag from open windows only showed a slight increase in the coefficient of drag for a vehicle. THis will effect fuel economy less than 1%. However, AC can affect fuel economy and power up to 10%. The main enjoyment of real windows is you can cruse in your car and wave and talk to people just like other classic cars. You can go thru a drive through and get your food without opening a door. You can also drive with the window down and enjoy the fresh air. As for the cost. The main reason it is so expensive is because the parts are custom made. If enough people wanted do this, the cost would drop significiantly. Probably to as around $1000 per door. It seems like a lot of money but driving a D with real windows is a totally different car. BOB