In some of my earliest moments in "advertising," I worked for Montgomery Ward as a copywriter in their catalog division. This was every bit as bad a job as it sounds. It involved a lot of "grinding it out," page after page after page and not a lot of creativity.
Nevertheless, I did get paid to write. I had to write to spec. I had to work with buyers (who were essentially clients) and I had to sell my work, usually under a great deal of pressure. I also got to work with art directors, print producers, typographers and editors. All of that was valuable.
Perhaps the most important thing I learned on this job, however, was none of the above. This is something that happened twice a year in which the buyers would report how much revenue they produced from each of the catalog pages we created. We would breakdown their page, and indicate that this item earned $47K, and that earned $88K and so on.
What I realized early on is that buyers essentially "bought" a page for, say, $200,000 from the company. They, therefore had to sell $200,001 off that page for them to keep their jobs. And, of course, for me to keep mine. What's more, if that page earned, say, $400,000, the buyer who bought that page for $200K, would get a huge bonus.
It occurs to me in looking at the world that landing pages and websites aren't all that different from catalog pages. That is, the things in the most prominent positions must earn you the most money or at least the most eyeballs. If no one cares or no one spends, you're out of business.
Like the buyers at Montgomery Ward you also need to learn that putting more shit on page, more stuff to sell, doesn't mean you sell more stuff. Best Buy has many more SKUs than Apple but does many fewer dollars/sq. ft.
I'm sure there's a mathematical way to calculate the "cost" or at least the opportunity cost of owned media. And therefore you should be able to say how much you should earn from each pixel. This doesn't seem that complex to me. I'm not sure, however, if anyone does this.