Amongst the most successful subscriber paywalls is that of the New York Times, boasting about 5 million paid subscribers.
Given about 130 million US households, this means that 96.67% of the country's households lack access to this source.
And before any comments on the merits or failings of the source in question, again this is among the most successful and widely used subscription paywalls extant, and it excludes over 95% of potential readers.
The exclusion cost is absolutely immense.