3k that's a lot
They told me a use one is 500
What kind of shop are you going to? Sounds fishy x 20.
They could just "pretend" to swap out your transmission, and then just replace the transmission fluid to make it run a little better. Charge you $500 for replacement, $500 for labor and in reality, the fluid replacement just cost them $20 and about 30 minutes of their time. Then, when the transmission breaks down again, they'll just blame the problem on the used replacement transmission and not knowing it had problems, when in actuality, it is still your current transmission giving your problems.