I think the idea of "high intent" is the same fallacy as the notion of "affordable." We say something is "affordable" because we have "enough" money to buy it,

I think the idea of "high intent" is the same fallacy as the notion of "affordable." We say something is "affordable" because we have "enough" money to buy it, but that's not how people make decisions in aggregate. The reason economists talk about opportunity cost is because people are constantly optimizing decisions based on new information. (Humans may not deal with prices and numbers very well, but they're pretty well evolved to break time into chunks and work out plans to solve problems.) If you talk to an individual, they might say "I can't afford it," or you may talk to someone who didn't click through and they might say, "I was just browsing." The fallacy behind both is you're creating archetypes and assuming they represent the modes of the population. And even if you talk to the individuals you based those archetypes on, there is a whole history behind how they arrived at "I can't afford it." Those changing circumstances are why the aggregate behavior doesn't show some arbitrary level of "affordability," and instead you see a smooth curve of consumer demand. And the opportunity cost of continuing to view a web page will not have neatly quantized levels of intent, but rather individuals have a broad array of competing interests.