The difference seems to be whether its social or alone. I've never spent anything on microtransactions/f2p, but I've certainly spent money on alcohol. It's a world of difference spending $100 in a night with good friends, and $50 on a night alone at home.
Alcohol recovery meetings are absolutely full of people who have to say "I thought if I wasn't doing it alone it wasn't alcoholism." The social context of use is only one factor, it can't be used by itself to determine if the use is a problem.
