If your car breaks, or anything else for that matter, it's normal to know cost upfront. If you any Aamco center you will be listening to a phone script. It has rebuttals for every question or argument. They totally avoid giving you prices over the phone. Why? They have been in business 50 plus years. They should know what the job will cost, at least the big question. What's worse case scenario. They have multiple rebuttals for this. Of course this is where you can be hooked to fix it. A highest price can be given to you. They just try not to. This is because their pricing is higher than anyone else.
The worst case would be replacing the transmission and one phone call to their rebuilding supplier and you could be told what that would be.
But rather than tell you this you gets loads of rebuttals why you should let them remove trans and tear it down. Once this happens, your pretty much at their pricing mercy. SO NEVER LET THE WORK ON YOUR TRANSMISSION WITHOUT A MAXIMUM COST GIVEN IN WRITING FIRST.