For me personally, I'd never spend that much money on a rebuilt tranny. I can buy one out of the salvage yard with <30k miles on it for $750. I can install it myself, but even if I had to pay a shop to do it, book time for labor is 6.4 hours, so even labor isn't all that bad. I can't see spending more than ~$1200 on the whole job if I sent it out to be replaced.
Most larger reputable salvage yards guarantee their parts, and in some cases, even guarantee the labor if the part fails within the warranty period. I've hardly ever been let down buying used parts.
I see nothing to gain from having a tranny rebuilt for more than double the amount of money only to keep the vehicle for another maybe 4 or 5 years. A buddy of mine had his tranny rebuilt in his Bonneville less than 4 months ago for upwards of $2000 and now he's already sick of the car and ready to trade it in. All the money he spent on the rebuild is going to get tossed out the window...The car isn't worth one cent more with a rebuilt tranny in it than it is with its original one, provided it still shifts fine.