They can also be used as little drill guide bushings for a #45 or #46 drill bit bit (depending) (at least the few I just measured). Or if you could manage to drill/tap for a tiny allen screw in the side, they could be a depth stop for the little drill bits. I really do think this way all the time, when looking at stuff like this. It's a curse.
I'd get some small cans, write "please donate string ball ends here", go into the music stores and ask if you can leave the can on their counter, and if it gets half-way or fully filled, you'd give them such and such amount for it.
Guys putting like 20 of 'em in an envelope with a 43 cent stamp (or whatever a stamp currently costs, I can't keep track) seems a bit extravagant to me, at least.