It would be cheaper to buy a foreign used one but it's a risk you're taking, since you really don't know what conditions it would have been exposed to. For all you know, it could give up the day after your warranty expires!
Alot of mechanics, even reputable repair shops (no name callling) claim that they are transmission specialist and days after people rebuilt their transmissions, it fails.
So far I like the work done by Chaguanas auto supplies
i rebuilt one in november 2010, and in early 2011 it went tru...i ended up buying a Foreign used one...and it still works fine! i guess when you dealing with used parts...you take a chance...