I'd be willing to pay probably $0.25/article for what I read on NY Times and Washington Post. I'd be willing to pay anywhere from $0.50 to $20.00 for many of the answers I come across on Stack Overflow (depending on how certain I were before reading the answer that it would actually solve my problem... plus how long the problem would take me to solve on my own and whether I can find the answer elsewhere) since I can directly see how that contributes to my productivity at work (and because I'd be able to charge it to my company).

Side note: In general, I actually wish there were more ways to pay per article. I really want to pay for people to write good content and it scares me that many great content creators of old are going out of business in the digital age. The problem is that for many sources, I'm not interested in a subscription to their entire repertoire since I only want an article or two.