Most expensive: Laser welders. Neutec makes one with a built-in binocular microscope. So expensive that my catalog does not list the price. You can also lease them.
Arc welders: ABI makes them for tiny welds. $3000-$5000 USD.
Water torches (no kidding -- hydrogen and oxygen is electrolized from the water) $1200 - $2300. Flame comes out of what looks like an injection needle. Good for places that are fire zoned not to allow tanks.
Smith Little Torch kits and other oxy/acet/propane micro torch kits, about $100-$300 plus cost of tanks and regulators (I am able to use normal full size regulators and tanks). Smallest flame of the oxy/acetylene model has .006 inch orifice size.
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