Here's a comparison. With advertisement sales, often companies will say you must provide at least X impressions, even if we won't guarantee premium pricing for

Here's a comparison. With advertisement sales, often companies will say you must provide at least X impressions, even if we won't guarantee premium pricing for you. Sometimes, maybe even most of the time, you'll get a high CPM (like Uber Black). Sometimes you'll get a low CPM (compare this to Uber X). Regardless, you have to do X amount of business with them or else they drop you. Sometimes this means taking higher quality traffic (thus potentially higher CPM), and funnelling it to a certain advertiser at a lower rate simply to maintain your impression level. That doesn't make web site owners, employees of ad companies even if they're solely dependant on a single ad company for their livelihood.