Its never cheap when getting driveline work done. I paid $300 each for mine but it was a heavy duty splined shaft driveline. I needed some strength to hold up to my 38.5" Swamper SX's, 5:89 gears and detroit lockers.
A standard driveline with new u-joints will be about $200-250.
Some 4x4 junk yards will let you look around and measure some used ones or have them cut a longer one down and weld it back up. Then take it to the driveline shop and have them ballance it. This is what I did for the front driveline. I took a rear driveline from a F350 so I had the CV joint (double u-joint) on it, cut it and rewelded, then ballanced. You will want a CV on both the front and rear drivelines for no vibration problems with a 6" lift.