I think Ford sells them new for about $250 each. Ask your dealer for the best price, many will sell to you at a little above cost especially if you bought your car from them. And Ford, at least my dealer, doesn't charge anything for shipping. That makes the price really great.
I am guessing that if list price is $250 each, you should be able to get the complete set at a discounted price for $750 or less.
I personally wouldn't pay much more than half price for a used set.
Check with your Ford dealer for his best price before you buy.