When I stopped smoking more than 10 years ago I immediately had a surplus of 300 EUR free cash per month. Two packs a day at 5 EUR per pack at that time.
Being healthier, not stinking like a wet ash tray and having more and better sex are other features of stopping smoking.
Yes to both, it has unfortunately led to an increase in crime, because they're so readily stolen. It has definitely led to a decrease in smoking as well, as a lot of smokers quit for financial reasons.
It's perfectly legal to grow your own, interestingly enough, but not many people do.
Not really a black market for cigarettes here but you can grow your own tobacco legally if you really want to go down that road. Smoking tobacco in younger generations is very rare but vaping on the other hand is very popular. The government was touting a "smokefree by X" date that kept moving back as the dates came closer.