One of these cream whippers came into my hands recently. It came with a box of 10 chargers, where 1 was missing. I speculate the owner used their new cream whipper once and decided it was too much work to clean. After ~20 years they gave it to the non-profit's yard sale, where I found it.

One charger cartridge is good for maybe a pint of whipped cream. You'd need 4+ chargers for a gallon of whipped cream. A restaurant could easily go through 50 chargers a week.

https://www.amazon.com/iSi-Professional-Whipped-Cream-Charge...