I believe Chicago is now the most expensive, outstripping NY by a dollar or so. As to variance, when my daughter was in high school in Jackson MS, I would stock up for about $4 a pack. For college in Houston, it was in the $5 a pack region, which was still a bargain. I always stuffed whatever I could into my luggage on those trips for the return trip home.
NYC is now a minimum price of $13 last I saw. I remember it being ~$12 when I stopped. If you're in a captive audience situation like commuting through Grand Central station and need a pack on either end of your commute, Hudson News, which seems to be in every airport and train station, will nail you for $16.
It's why loosies are common, but illegal, in some neighborhoods in NY. There was the famous case of Eric Garner who ended up choked out while being arrested for selling loose cigarettes.
my son is in the Houston area and says cigs are around 7 dollars a pack now for name brand..