you could easily pay 40 dollars by the time you buy those pieces seperately, its not a bad price, the real difference is that if you bought them on your own the price point is how fancy you decide to get on the riser wood. I get Ipe at a decking supply store at 3 dollars a foot. 18 dollars for a board that will make at least 3 bows with my meager skills (sam harpers site shows him getting 6 bows from it) is awfully hard to beat.
is the kit already glued up? don't forget the expense of buying glue. TB3 is pretty cheap, and for a hickory backing will work fine. But i am a real fan of boo/ipe. get you some URAC 185. you don't need a hotbox.
20-25 dollars for glue, 18 dollars for ipe, thats 40 bucks right there, without the backing, riser or tips...but if you get it yourself you can easily make 3 bows for the same price (i know i am not figuring shipping)... just something to think about, cause you know you won't end up making just one...thats why we're all one here;)