Early in 2012-2014 I worked for a SaaS paywall provider that offered what we called a National Model. You would pay once and get access to all major newspapers in the country. The fee you paid was divided into provider fee/a reward for the newspaper you bought your subscription at/time spent reward divided by user behaviour.

The company has a successful business selling single instance paywalls. Why? You're in essence asking competitors to cooperate. One of them has higher costs and needs to raise the price? All the others need to agree on it. There's all kinds of complexities in this kind of system.