Assuming you can find someone who wants to buy a one-off carton of foreign smokes for full price from some stranger
Anyway I’ve never noticed anyone declaring their cigarettes at customs so I think it just one of those rules that never gets enforced.
I believe what's been lost is the "booze cruise" intra-EU option (where tax has been paid elsewhere in the EU) where the limit is "for personal use", an incredibly vague limit where the onus is on you to convince customs that you have no intent to sell.