I have only the “anecdote” that among alcoholics I’ve known, success at sobriety was very strongly correlated with AA attendance.
I’ve already mentioned one woman, sober for the last 30 years of her life, who became a very successful life-saving counsellor and, despite having strong will-power, still insisted on attending meetings because she “needed to.”
AA claims to have 2 million members. $5 per member is certainly “small potatoes.”