Every quarter, another headline screams that the vape market is worth $XX billion and will double by 2030. These figures get quoted in investor decks, supplier emails, and even some shop-floor conversations. But what does that number actually mean for you, an e-commerce operator trying to decide how much inventory to buy or whether to expand into a new category?

Honestly, not as much as you'd think. Market size estimates are built on assumptions—sometimes reasonable, sometimes shaky. The first thing to ask: is this measuring devices, e-liquid, or both? Does it include gray-market sales? Which countries are in scope? Different definitions can swing the number by a factor of two or three.

That doesn't mean you should ignore market size altogether. It's useful for spotting broad trends and validating a segment. But treat it as a starting point, not a fact.