I bought some from Rockler way cheaper than that. I think they call them threaded adapters? Can't really remember, but they do have them and I'm thinking they were like $6 or $8 bucks for a bag of 6 or 8 inserts? No where near $3 bucks a piece! Wow! Are they made of silver or platinum.....LOL
I actually believe the ones I bought are stainless? I'd have to go check, their in my toolbox.