They are about $13 a dozen from the website. Three packs are about $6 at a local store (Harps). About the same price as a lot of flies, but they last a lot longer than flys.
There are several sizes of fly rod jigs (1/124, 1/80, and 1/64 oz Ithink) and 1/32 ,1/16, 1/8, 3/16, and 1/4 oz. in the spinning sizes.
I have no idea why the trout eat them with reckless abandon, but they do.