> You need readership in the millions to make this model viable
Not necessarily; for primarily online publications, operating costs rise roughly linearly with readership. I operate a donor-supported publication with a much smaller readership than the Guardian, yet we have stayed afloat for years via donations because our costs are much lower. It's a model that can work for practically any size of publication.
Your publication cost are roughly linear; your content creation costs are more or less constant with an increase in number of readers. I would assume that your content creation costs are vastly lower than the Guardian's which is why you can get away with fewer readers. You wouldn't be able to produce content like the Guardian on your budget, though.
Not necessarily; for primarily online publications, operating costs rise roughly linearly with readership. I operate a donor-supported publication with a much smaller readership than the Guardian, yet we have stayed afloat for years via donations because our costs are much lower. It's a model that can work for practically any size of publication.