I want to start by saying I am a huge supporter of fly Shops, and try to buy all my materials from a local shop. I haven't had a fly shop that carried fly tying supplies in my town until just recently. Because of that I ordered mostly online, and mostly from a fly shop in the western U.S.
I will say, tungsten beads at fly Shops are ridiculously priced. I have not bought many beads from fly Shops for a long while now. 20 beads for ~$9 is crazy. That is almost $.50/Bead! I hate to do it, but you just can't beat amazon for beads. Most 50 packs are ~$16, lowering it to $.32/Bead, and if you buy in 100 packs they are ~$22, or $.22/Bead. 200 packs are available even, dropping the cost to $.185/bead. I should say this is based on a 3.0mm bead, and I realize the price goes up for larger sizes (and down for smaller sizes). They have all the colors and sizes, and are delivered to your doorstep usually overnight, or at most two days later. I have not noticed any difference in fish catching since using off brand slotted beads from Amazon.
But, I do hear your concern. The Amazon prices have recently gone up as well, and there are not as many next day shipping options...might be more like a 5 - 7 day wait. Still though, I can be patient to save myself around $.25/Bead.
Will tungsten price itself out? It would be a while for me. If you look at the cost of a, say, sz. 14 tungsten jig Duracell fly your looking at $3.80/fly. The other materials for that pattern are relatively cheap, and i know mine won't fall apart after a couple fish, so it would take a lot for me to not tie them for myself, even if I did end up paying $.50/Bead. And, I prefer to tie my own patterns rather than fish the same ones everyone else is fishing. Plus, I would guess the fly cost will go up as the bead cost goes up.
I mostly fish dry dropper in the summer, maybe i'll do an experiment this year and see if my fish catching changes with brass beads. I have a ton of those that I basically just stopped using once tungsten came out. However, while brass beads are still cheap, I can't find any slotted ones, so that limits tying on jig hooks...
Probably not the answer you were hoping for, regarding purchasing on Amazon, but I just can't bring myself to pay extra for beads that don't change the flies that catch fish for me.
Out of curiosity, do you think tungsten beads catch more fish? Another way of asking that would be: before tungsten beads, did we catch less fish? Or did the introduction of tungsten beads make it easier for people to catch fish? Do tungsten beads make us better fisherman? As mentioned above, this makes me curious, and I might do some self investigating this summer to see what a life without tungsten beads looks like!