I believe that these claims are not really lying or exaggerating so much as purposely misleading...What irks me about the mini-mart/mall kiosk PVs is the false advertising. They say that a single cart is like a pack of cigarettes, and that's not just misleading - it's a flat-out lie.
I think what they might be doing is saying that a cartridge has as many milligrams (mg) of nicotine as a pack of cigarettes.
So therefore if you ignore the possible fact that we absorb far less nicotine from using electronic cigarettes as compared to cigarettes, you can potentially say that a cartridge could equal a pack of cigarettes. Of course, that is only if you consider that you would have to be taking only like two drags off your electronic cigarette and pretending that you have just smoked a cigarette.
So yeah, if you only take around two drags every time you would normally have a cigarette, it may last as long as a pack.
And if you absorbed the same amount of nicotine from an electronic cigarette as you do from a real cigarette... there's your one pack.
Notice they never actually say it will "last as long" as a pack of cigarettes, though.
They always say it is "equivalent" to a pack of cigarettes.
And that's probably true, as long as you conveniently ignore absorption rates.