Apparently, there's an Amtgarder around here who has a "friend" that needs to get rid of a whole bunch of bamboo plants, so he's going to harvest them, dry them himself to make it "weapons-grade," and then sell it to other Amtgarders. The price? $15.00 per stick. Instead, I looked online for other options.
Cali Bamboo sells 10 foot long, 1 inch diameter poles for $2.25 each, but you have to buy 25 of them. I also don't know how much shipping costs. However, it appears you can also buy bamboo fencing and then separaate the poles, and according to my calcualtions that's actually a little cheaper than buying the poles separately. I don't know whether they're dried or not.
Bamboo Supply Company sells bales of 50 poles that are each 8 feet by 3/4 inch diameter for $48.50 per bale. That's about $1 per pole. Even if shipping is really expensive that still beats the $15 per pole. And this web site specifically says the bamboo is dried. I think a good strategy would be to buy a big bale, and then go to an Amtgard event and sell them. If people are really willing to pay $15 each, I see a very wide profit margin opportunity here.