Have you thought about rebuilding it yourself? They aren't that hard once you know the steps and measurements. Not sure what tools you have as there are a couple specialty tools you would need, but the difference in cost between doing it yourself or someone else doing it, would be covered in that difference.
There are a lot of guys on this forum that can walk you through what it takes. The main thing you will need is patience in setting the measurements correct. For the first time, you would need to budget a full weekend and at least a 12 pack...
Just an idea... Not everyone is comfortable doing a rear end or trans rebuild. Mostly it is due to being nervous in doing something new. But as for being nervous, it will increase the focus to do it right.