Most people will choose free with ads, but a significant amount will chose premium if it is compelling enough and that can represent a lot of money.
Ultimately, I think people are very charitable when it comes to trivial transactions, but not when they're inconvenienced, and so I think it would be best for everyone to make that usability gap as tiny as possible. Even better if you could actually get something for your quarter: stats showing your tip% compared to peers or friends? Different site styles for high tippers? Personal stats tracking your interests over time? Monetized, unskeezy, free-as-in-freedom "likes": lots of possibilities here.
Many people? I don't think it's a lot. Look at the subscriber numbers for Netflix. Or consider how many are willing to sign a contract for their cell phone. People will pay if the value is high.
I think the truth is most people don't care very much about the news. Time is scarce and people have a lot of choices about how to spend their time.
And yet, people are more than happy to tip a busker or leave a few bucks for the waiter or bartender. (Even outside the US, where tipping isn't expected.)
Netflix and Spotify are giving people something they want without a lot of friction. I can get everything on those services for free other places but the experience is worse.
People are tipping buskers because they are sharing a physical location with that person. Put the video of the street performance on YouTube with a tip button and the dollars per view number is going to drop drastically.
Bartenders and waiters are tipped well because they are providing personal service.
I haven't heard a subscription news model which doesn't feel like its also trying to sunk-cost me into being less critical of the reporting.
Subscribing to multiple services isn't that unusual. There just has to be some value to it.