There will be exemptions for legitimate uses of nitrous oxide, for example in medical or catering industries. The gas is commonly used as a painkiller and for producing whipped cream in cooking.
It’s in no way unfeasible - and the deposits end up paying for the ongoing operation of the system.
Which is better, addressing the littering problem directly, or criminalising and litigating against a bunch of people with a law that can’t be enforced if they have a can of cream on them?
The deposit is just a deposit, it doesn’t pay for anything. Are you sure you understand how the deposit in this case works? You pay for something and you get that back when you return the item.
Maybe you should look into something like the Finnish bottle deposit scheme. It’s great but those take quite some time and effort to set up and get running properly.
Not everyone returns and collects the deposit back, these deposits end up funding the operations.
If the Finnish scheme is anything like the German scheme, that’s what I was thinking of. Although it doesn’t need to be quite so widespread with machines inside every supermarket.