Want to make your own Large, Demonstration, or standard Go equipment inexpensively? Here are some internet resources for ordering parts and raw materials in the United States in low quantity. Comment below if you order and create!
If you have a qualified teaching program (supporting teachers and organizers who want to teach Go to children in school, after-school programs, libraries and community centers), the least expensive place to get ready-to-play sets for playing is the AGF. The demonstration equipment, however, can be DIY'd for less using the suppliers below.
The least expensive ready-to-play full-size set seems to be this one at Amazon ($16) also available online from Toy and Game Warehouse or Target.
The least expensive stones are, you guessed it, the "Anti-bacterial Hi-tech" stones from YMImports. All of the options for stones are close to the same price.
Plastic: Toy and Game Warehouse
Glass: Wholesalers USA (17-19mm, a little smaller than standard)
The currently least expensive wood/magnets are at Woodworks: Ceramic magnets glued to wood (magnets are 1/2" or 3/4", wood is 3/4" - 2-3/8" flat or domed). For example, the cheapest combination at 1-1/2" demonstration stones would be the 1/2" magnets and the 1-1/2" wood discs coming in at 17¢ total per stone, or 21¢ if you get to the $75 for free shipping (upgrade to the 3/4" magnets, get an extra bag of 100 discs, or E6000 glue). If you make more than one full set of "stones", you can get it a little cheaper. Total cost would need to include glue and paint.
Round flexible magnets are about the same as the ceramic above (10¢)
Wood types: flat, domed, round plug from a variety of vendors. All of these sell bulk at pretty decent prices.
Magnets from a few vendors. Most seem to be "Master Magnetics" brand.
Blank Wood: 13x13 Blank 11-7/8 board ($2) (this is quality B/BB which will have some blemishes on both sides).
Plastic: Chess n Games ($10)
Wood: "ORIENTAL WORLD ARTS" through Amazon ($20)