It actually costs $7-8 if you buy the parts in small quantities at retail stores. The brass tee, the npt fittings, the bolt, and the nut can all be found at home depot, or better yet at a good hardware store. I had to go to the hardware store for the spring and the tap, and as they were out of ball bearings I had to go to the bike store to get those. You could do it with a trip to a well-stocked ACE. The expensive part is the tap, that takes it from a 7-8 dollar cost to around a 14 dollar cost, and I haven't seen any fittings that would work without being tapped out. If you don't count that as a general tool cost (which I do) then it's more like 14-15 bucks.