There's more problem with per-article payments than transaction costs. E.g., how I know if I want to pay for particular article - maybe it's a useless crap that isn't even worth my time, let alone money? I could pay _after_ reading, but then the publisher has no guarantee I would bother to, after all I've already got what I wanted.

You'd say "well, NYT is so good you would want to pay for _any_ article published there!" - but then why wouldn't I subscribe if I value them so much?