I've got two of the cams and one tach drive and one tach (you need a 650 tach too). I paid $65 for one of the cams and I can't remember what I paid for the other but it was about the same and the 650 tach (could be in a lot better shape) came with it. I bought the tach drive gear separately, it cost me $35.
So I'd say that your $100 price sounds about right. Just make sure you mike the cam lobes (and inspect the journals) before you buy it.