Micropayments have long been touted as a solution but nobody has really implemented them widely. You would think credit card companies would be in a good position to do this but their system must suck. In fact, they keep raising their transaction costs to the point where vendors often charge extra if you use a credit card. Maybe that's just the banks being greedy. Crypto could be a solution but it will definitely take something like hive which has no transaction costs.

Honestly, I'm not sure why traditional advertising techniques can't be at least a partial solution. You don't need Adsense spyware or similar, just an ad department (one person really) who manages selling ad space on the site. This could even be automated. Static banners with a link should work better than newspaper ads did since the link is right there for impulse buying.