OpenAI has already started degrading their $20/month tier by automatically routing most of the requests to the lightest free-tier models.
We're very clearly heading toward a future where there will be a heavily ad-supported free tier, a cheaper (~$20/month) consumer tier with no ads or very few ads, and a business tier ($200-$1000/month) that can actually access state of the art models.
Like Spotify, the free tier will operate at a loss and act as a marketing funnel to the consumer tier, the consumer tier will operate at a narrow profit, and the business tier for the best models will have wide profit margins.