Value received: Reader gets content to view/read. Price paid: Advertisements are pushed with content. Market Evaluation: CPM
The more advertisements and advertising 'gimmicks' (click throughs, pop unders, talking flash) that readers deal with raises their perceived 'cost' of the content.
The more Ad clicks, views, mouse-overs, demographic sharing/tracking the web site gets increases the revenue generated by the content.
Costs associated with generating the content - CMS operation, rights clearance (author, images, other media).
There is lots of evidence that as people put more and more intrusive advertisements on their web site readership goes down (higher 'cost') and mitigation efforts (AdBlock, Flashblock) go up (user attempt to lower the cost). Interesting experiment at Ars with blocking content if Ads are blocked: http://arstechnica.com/business/news/2010/03/why-ad-blocking...
Versus the paywalls (very explicit cost structure for readers).
All this adds data points to the questions of 'can readers distinguish between good content and not-good content' and what is the marginal value of 'good content' vs 'farmed content'.
Really fascinating to watch these systems getting tested and evaluated in real time in the real world.