You mean well, well under $1k... like $65 and some craiglisting. You can have a soda machine that will be somewhere between $0.08 and $0.15 cents a liter to operate.
If you can find a commercial soda machine/gun kit for $65 I would by it on the spot. The operation costs are super cheap, which is the point, but I haven't found the equipment anywhere cheaper than around $800.