Well it cost me 115 bucks for 2 ujoints and a ball and socket... 50 bucks for the ujoints and 55 bucks for the centering ball... You might get it for around 30 dollars, I know others on this site stated thats what theirs cost.
The thing is, my double cardan seemed great when I pulled it out. I had a rotational squeak and a rotational clunk noise... I knew the squeak was from the double cardan because it would squeak when I would move the shaft with my hands, the clunk on the other hand resolved its self after I fixed the joints. I have 180,000 miles on my truck and Im sure the double cardan has never been looked at.
It might not be the double cardan though... I would grease the slip yoke first Ive read those squeak sometimes, greasing the slip yoke is easier, and cheaper, than replacing ujoints and the centering ball.
Hope this helps...