Well, the “P” guys buy from Stoddard, but Pelican Parts (where I got mine) have them for half that price. Just don’t go too cheap on them (like from eBay) because the el Cheapo versions tend to be soft and strip the threads when tightened. $150 - 175-ish for a set of 20 sounds about right.
The good ones will take 100 ft. lbs. of torque without stripping.