Sounds pretty good to me for a full rebuild, revalve and respring... that's the whole enchilada $625, springs are around $100 each end as you mentioned and then seals oil etc adds up, so a couple hundred for labor seems pretty damn cheap to stay in business! Especially messing with the valving.
I found this video series pretty good on changing for seals if you wanted to tackle it yourself, just pop the new springs in when you put it back together:
http://www.youtube.com/watch?v=W2G-b66F3es but it won't be revalved.
My bikes new so I don't need a rebuild and I suck so I don't need a revalve, but I watched it so I could get an idea on how to put heavier springs in myself since I want to do it on 3 bikes. Spring on the rear should be a piece of cake:
http://www.youtube.com/watch?v=wLZLcElWb7E