I don't think that cost is the main reason for getting this product. It's just convenient to always have soda water here without having to carry it through the city.

I recently bought one for convenience reasons (after i learned about th glass caraves) and am totally happy with it - I guess as more (young) people in the bigger cities don't own a car (and only buy small quantities of food in the supermarket around the corner), more will use products like SodaStream.