Both all-you can eat, apply to any publisher, and some sort of (waves hands) standard pro-rata scale. Probably scaling down with higher volume (RMS suggested a log-of-views basis, because reasons).
In both cases, I'd like to see the reader/viewer fee scaled at least roughly by income/wealth.
Ad-supported "free" seems to have won.
There was a brief enthusiasm for tacking small payments onto mobile phone bills, but that never really caught on.
The trouble with micropayments, I used to say, is that all the enthusiasm for them comes from people who want to collect them, not pay them.