If the purchase is for the workplace, even something recreational for the employees, the company should pay for it. There should be a fun-budget for such things. Group purchasing is still an interesting idea, I just don't think the example's a great one.

A lot of workplaces don't work like that! I know my small non-profit can't go buying appliances, but we recently went in as a team on a sodastream and it would have been great to have a system to track it more than someone putting the cash up front.

FYI, there are mod kits for sodastream machines to connect them to large CO2 tanks. I installed one on mine recently, love it so far.

That may incur tax liabilities and in non-tiny workplaces purchasing anything is a huge hassle.