I have seen them for sale from anywhere from $750 to $1300 for a complete suspension. Bender has a kit that is $1000 w/ a different shock that doesnt use the adjuster, but you reuse your rails and idler wheels. I have about $60 in brackets, rivets, and bolts.
I took me close to 10 hours from start to finish, but I replaced the track at the same time. You need to cut or drill out about 1 million rivets. the stock rear bracets were in the way so they had to go. the right mid bracket was in the way of the adjuster, so i took them both out and used them for the front mounting point.