One of my websites is part of a large health vertical from a direct advertising company which sells some of our ad inventory.
There are several websites with UGC like my site in the same vertical and the same niche but no other site in this vertical even comes close to what I earn with AdSense on my given traffic.
In particular there is a health website receiving over 4 mio pageviews / month (editorial content) which is nearly 10 times the traffic I get (UGC) but they roughly earn 2 times my revenue only.
Traffic and content has its influence on earnings but two sites with the same content and traffic can have major differences in revenue even if they occupy the same niche.
I am not a complainer, I do my best to constantly optimize my business.