I've actually given up smoking now (after many years) for health reasons.
I used to buy a cheap flight somewhere for the day, Brussels, Paris, Geneva etc. I live in London so easy to get to the airport. I'd have lunch in the city, then load up at duty free. I'd buy 10 cartons (10 packs per carton), fit in a small carry on case. That would last me several months. Cost including flight and lunch etc would be around £500. To buy them here, £1500. I did that for about 10 years (covid period aside). Also used to bring them back when I actually went on holiday.
Technically you're only "allowed" one carton but that's only an issue if you actually get stopped by customs. I never did. Most times there weren't even any officers at customs to stop people!
I don't know anyone who has paid full price in a long time. Personally I wasn't keen on "under the counter" as you can't be sure of what you're getting. But I know a lot of people do that.
So ultimately, the higher the prices go, the more of a black market there is. The more people like me just go and get them from abroad. Which means we're paying zero tax on them. As I say, I've given up now so doesn't matter to me but there is (well has already been really) a point where a higher price is counter productive.