I suppose it could depend on the estimated number of parts required. One shop may be quoting based on anticipated hard parts they plan on putting into the transmission. This might be indicated by differences in warranty from the two shops.

I rebuild T350's and 700r4's for around 200 labor and 150 in parts, because they just dont break hardparts. On the other hand I wont touch a Ford a4ld for less than 800. From experience you have to use a brand new valvebody from the factory in order to insure the darn thing will work. My cost on the valve body is 250!!

Ford Taurus invariable breaks the forward planetary, which of course kills the transmission. That part alone is $150 cost. Average parts used on one of these transmissions is $400. The average repair shops charges $2300 installed.

I hate to say it, but automatic transmissions are usually very simple and easy to rebuild by someone with average mechanical skills and a good tech manual. The required tools are not always special and fabricate most of them easily.

A good example are the rubber piston rings used in the clutch packs. GMC has special cylinder tools to compress the rings and fit the piston into its bore without tearing the piston ring. These tools cost over 200. However, you can use a simple thick rubberband to compress the piston ring. Then stick the piston in your freezer for 1 hour which you are doing something else with the trans. You can then simply remove the rubber band and drop the frozen piston literally into the bore.

Hehe this is probably more than you wanted to know. but if you are able to do it yourself you can save around $1000.