Barter economy is a myth. If you think that's wrong, do a mental exercise -- try to imagine how that would work in practice.

We never, as a species, had any meaningful instance of barter economies. We've had the concept of debt since before we had currency. I imagine this is what we would try to "return" to if cash disappeared, and people needed to exchange goods and services without authorities and intermediaries. This would though require a community, a social fabric -- something that has been steadily eroding for a long, long time.

Some rural communities already do this and have small private forums restricted to the locals. That does not exclude using cash, it's just another method of trade to fall back on or to use when it makes sense. If the internet is down they can all meet in a church parking lot or someones field.

I doubt it. Barter economies didn't have cellphones, PayPal, M-Pesa, Pix, etc.

Cigarette cartons are an unintuitively good currency object. They're high-density ($/volume or weight), storable, non-perishable, sub-dividable ("packs" in "cartons", I think that's how they're subdivided?). They're easy to count. They come in standard, audited sizes, the trusted-brand manufacturers certifying their weight (?) and stuff. The large population of tobacco addicts guarantees a stable demand, hence a stable value.

e.g. https://www.washingtonpost.com/archive/lifestyle/1987/08/29/...

(From a 30,000-foot view, it's kind of analogous to cryptocurrency. In a failed state, you don't accept cigarettes as payment because you want to smoke them—but because you know you can exchange them again to someone else, and to someone else, eventually reaching a smoker, who creates the demand sink. Similarly, people accept cryptocurrency units because they know at the end of the commerce chain, there will be drug dealers guaranteeing an intrinsic demand).