I followed this guys writeup, however instead of the metal rod, I used 2x4's. Note that the pictures aren't of mine.
I used steel cable, 8 eye bolts, 4 little pulley's, 7 cable clamps, a couple of longer 2x4's and 4 small 18" 2x4's across the roof rafters in the attic to make sure I had it up there right, and a worm gear pulley that will hold the weight of the top x 10 and takes no effort to get it up there. It does however take alot of turns. I can't remember the exact cost, but I think it was about $80.