If heroin was free, nobody would be breaking into cars but there'd still be a problem.
I think we're missing the point debating addictiveness. meta very deliberately use patterns that result in compulsive usage - and at the scale they operate - cause a substantial amount of societal damage as a result.
They're also not doing that to pay for tobacco. Come on. Heroin is justifiably illegal for good reason already; you're stretching the analogy past breaking point.