The New York Times reportedly had 35.5 million pageviews in May 2013. Their "Snowfall" story reportedly got 3.5 million page views in one week but that was kind of an outlier.
In the first three months of 2-14, they had $290 million in revenue. Digital subscription revenue was $40 million.
So this isn't accurate for the NYT specifically, but if we suppose an NYT-type operation serving up 106.5 million page views every three months, they'd need to collect micropayments of $0.37 USD per page view just to make up for the digital subscription piece (they'd still be running ads).
Is that too high? I think I'd be much less inclined to click on NYT stories if I knew they were asking $0.37 per page view. That would be somewhat irrational of me because I can totally afford it, but that would be my cheapskate instinct.
Suppose the NYT removed their paywall and requested only $0.15 per pageview -- would they have more pageviews because more people could access them? Or would traffic remain constant?
It's likely that high-value web properties like the NYT would probably not see a benefit towards moving to micropayments, or perhaps they would at least keep the subscription model and experiment with a micropayment/paywall hybrid aproach.