I will never buy cigarettes online, and you shouldn't too ! You already take huge risks for your health, why looking for more problems?
Firstly, cigarettes sold on the web are sometimes manufactured disregarding any control and any standard of hygiene, these counterfeits can present 3 to 8 times more, arsenic, cadmium and mercury, not to mention the presence of textile fibres, plastic and who know what else!!!
Of course, there put plastic in cigarettes..
Most often they are produced at the regular tobacco factory. With all of necessary standards. High price different is because of lowest tax in some countries.
Secondly, most countries, if not all, forbidden selling cigarettes online. If you buy tobacco online, you are breaking the law, since you buy illegal products. What are you at risk? It is more likely that you will never receive your package if it is seized by customs.
This is what I say about the price difference. I am not sure about legality Tobacco-shop online business