How the fuck do you hit rock bottom solely on nicotine?
Tobacco, the main ingredient in cigarettes, is more addictive than meth. If you can imagine somebody hitting rock bottom on meth then it should be easy enough to wrap your head around it. Especially when cigarettes contain added chemicals to make it more addictive than tobacco alone.
Also, I would be inclined towards believing that the habit is mostly spread through peers. Price as a barrier to entry wouldn’t be effective at preventing peer pressure if they’re your first supplier.