What the hell is going on with shops?

Why didn't your shop just put the solinoid in then?

If you're a shop, don't you have a trans shop that you have an existing relationship with? From shop to shop they are more likely going to go off another diagnostic.

Nonetheless, it appears the original estimate was about almost double too high. But we still don't have an itemized list of that estimate to see what was included.

That is a good gut check. I still think in transmission repair industry there are wide price differences from shop to shop. More so than in general repair.

No I am not a shop, nor do I own one any longer.
I am retired from ASE and ATRA (Automatic Transmission Rebuilers Association) and owned an auto repair business in Cal and before that a service writer/forman/exotic trans builder for a national trans chain.
My Nephew will put it in himself with a little supervision just so he doesn't pinch a wire or something.:-)
He works in a custom fab shop for Dodge trucks and is very capable, but he thought he would just have someone elso do it so he didn't have to mess with it on his day off.
For $1,100.00 he'll mess with it. :-)

There was no written estimate, as he just asked if they would change it and they told him they would do it for that price.
Very likely just trying to get him to go away, since he already had his own parts.