Dave,
I bought the whole setup 5 years ago and it was $225. You can see the set up here. The aluminum arms are really heavy, so a carbon replacement is a big upgrade.
http://www.apsltd.com/c-947-selden-proctordinghymastboomspreaderparts.aspxWhat I am making is a carbon version of the arm - 450mm long and a bit wider, I took a mold off of a model helicopter blade that I modified, so it's wing shaped. You still need the barrell adjusters and the brackets.
I will get weights for you so you can compare the savings.
Bill