I also hate when people make claims like this without the explanation. The claims are only true if you compare the nicotine levels. E.g. assuming that 1 cart holds 1 ml of e.g. 16mg/ml liquid, the comparison of 5 carts to 80-100 cigarettes stands. However, smokers are only going to count puffs, and even that is the best case scenario. From my personal experience, most are just looking at the time period and comparing from there, e.g. 1 day = 3 cartridges = 1 pack.
On the other hand, the above is very is very subjective measurement. I have a friend who completely switched from 2 pack a day habit to 1ml of 16mg/ml per day, as well as the other one who switched from half a pack to 1ml of 24mg/ml per day. How do you publish that kind of comparison? Most suppliers publish nicotine contents comparison, since it is the only one that can be reliable.
I strongly believe that we should just accept that ecigs are completely different from analogs, and let the customer decide for themselves. That's going to be a bit problematic at the beginning, since most smokers have no ecig experience, and are trying to decide what to buy based on their current habit.
