Indeed. If you don't plan on smoking them, you have to sell the cigs to make this work. Flight costs $N, so you buy enough cheap cigs here and sell higher there so that you make $N back, plus commission for your effort.
The site is about mere 10 packs. Some jurisdictions allow the personal tax free import of even more than that. Within the European Union, for example, it is 800 cigarettes = 40 packs (200 cigarettes = 10 packs from outside EU). Assuming the "old/classic" size of packs with 20 cigs each.
It's worth pointing out that the personal allowance is usually for personal use, intent to sell does not come under personal allowance.
Usually this is near-impossible to enforce, but attempts to organise/aggregate these (which I initially thought this site was going to attempt) do raise your odds.
That will likely quickly make it impractical. How much you can make per unit is pegged by the price differential, where the only way to make more is via volume. The probability of getting caught scales super-linearly with volume, unfortunately, and the consequences also.
Furthermore, the medium in question (passenger flight) places practical limits on volume, and raises likelihoods for getting caught. E.g. a large suitcase full of cigarettes is much riskier through an airport, than the same amount of cigarettes tucked away among a lot of other stuff in the back of a 1 ton truck going over the border.