I got 2 set's off E-gay... One NOS set in the Cal Custom box, and one used.. The NOS one's were around 150..never on a car. the other one's i paid 75 bux for and there were 5 of 'em.. Check swap's and keep an eye out on e-bay..you'll find 'em eventually Rat...
I got mine off eBay, before the reproductions and the spider craze. They generally go for big bucks. I have the ultra rare 4-lug ones -- an NOS(!) set, and a beater set in good shape. I got them really cheap and never come across any other 4-lug sets.
i think the 4 lug vcaps are rare in the sense that studebaker flathead six speed parts are rare. rare, but also zero demand for them!