Note that Max is the $100/$200 per month plan; In addition to the obvious incentive to upsell, I suspect attempting to use Fable on the $20 per month plan would wreck your quota.

On a related note, Codex just reset their weekly quota, again.

Just a few requests of Opus on the $20 plan uses up my entire 5 hour limit... I don't even want to know what Fable would do.