When I changed my fluid in my Windstar 2 years ago I got Motorcraft Mercon V for 3.79 a gallon, at the dealer.
I think the guy messed up, so I asked if that was per quart, or gallon. He said per gallon,(It was in gallon jugs) so I flushed it and was happy.
I have since changed the fluid again with Mobil Multi Vehicle ATF.
(Ford Approved for Mercon V. It is the blend not the full syn.) It was a gift from a friend that works at an oil distributor. Otherwise I would have tried to buy it from the dealer again.