I began buying glass beads from JoAnn's because I was tired of paying a premium for metal beads at the fly shop. They also give a tier some more interesting colors to play with. But I've found that, whether due to the weight difference or the color difference, some of my patterns don't fish as well with glass beads.
But today I went to JoAnn's and discovered cheap metal beads I'd never seen there before. They are Blue Moon brand, and they come in a few different sizes (probably what I would use on size 16 and 20 flies, respectively, but I think they could be made to work from about 14 up to about 22). They have a large bore, so they would easily slide onto a hook shank, but the bore is not tapered, so you might need to half-hitch it into place to keep it from riding up over the eye of the hook if you were using it to tie a beadhead fly. The price: $3.99 for a pack with 120 beads, some the smaller size and some the larger size. Or, $2.99 for a pack of 200 of the smaller size. I didn't see the larger size sold separately, but it may just be the selection offered at my JoAnn's. I'm certain you could find all the colors and sizes online once you tried the beads to make sure you knew what you were buying. Here's a link, for example:
http://www.createforless.com/Blue+Moon+Beads+Crimps+Antique+Gold+120pc/pid150250.aspx?utm_source=priceGrabber&utm_medium=cse
Finally, in addition to bright gold, silver, and copper, they have these beads in several muted colors that would be excellent for more subtle flies. They call them antique gold, antique silver, and antique copper. The antique gold and copper are similar and look like those wonderfully oxidized beads you sometimes find streamside on flies that have been hanging in tree branches for a few seasons. The antique silver is a beautiful gun-metal gray. I'm pretty excited to try them out.
-Shawn