Cigarettes (and to some extent alcohol) are one thing I think should be very heavily taxed, and therefore very expensive. The high prices are intended to encourage people to quit smoking, and more importantly, discourage people from getting addicted in the first place. Heck, a handful of countries are finally starting to ban cigarettes altogether for people born after a certain year. This is good.
I know I’m speaking from a point of “privilege”, I’ve never smoked in my life and never been addicted to any substance. I know it’s just not feasible for some people to quit, and for them, the high prices really suck. But on a society level, I still think it’s better if cigarettes are expensive enough to remind you you should quit every time you buy them.
An extension is probably not needed. JavaScript and local storage allow you to do this kind of stuff. Proton Drive and Mail accomplish this without an extension.