I've said it elsewhere so I'll repeat it here. The trouble with comparing rebuild prices is it all depends on what all is replaced. A cheap rebuild may only replace clutches, steels, bands and gaskets.... a slightly better one might add servos and a new pump, an even beter one will replace the sprags (one ways) and maybe even the planetaries, esp the OD planetary. Finally you could go full out like I have in my Diary rebuild. Each has costs associated. And there is an element of trust in the shop involved too. People do not understand trannies so shops could, if they wanted, lie to you and you'd have no idea.
If you do not have a shop you can trust, it is my opinion your best course of action is to get a reman'd tranny from Ford. They are not cheap but they are more or less done right.... and have a good warranty. (Never thought I'd be shilling for FORD).
That said, there ARE some quality rebuilders out there, but far and away most do NOT do an A4LD rebuild like it NEEDS to be done - and which is WHY they have such a bad rep on rebuilds. Simply put, if there are NOT hard parts being replaced, it's likely not a quality rebuild. The A4LD needs more things replaced on a rebuild than the usual trannie. Simple as that. "Soft rebuilds" are another rebuild moved 10,000 to 20,000 miles down the road.
There. I said it, again. SO shoot me.