Along similar lines, we have a decent amount of senior (read "older") people at our company that are well paid. But, most of the work we do can be done by less experienced people who are much cheaper. That almost always means they are young. We don't discriminate based on age, but if you just looked at the ages of people that we mostly hire then that data would look like we're discriminating based on age when age is not part of the decision at all.
This is what I observe as well. If you have job that really just boils down to hooking up event listeners in java-script and fiddling with html and css until it looks they way the designers want it then experience beyond competency isn't really all that important. On principle, a company should hire an older dev with decades of experience if they're willing to work at rates that reflect the job they're doing. But devs with decades of experience are probably looking for work that is more complex and pays better.
Along similar lines, we have a decent amount of senior (read "older") people at our company that are well paid. But, most of the work we do can be done by less experienced people who are much cheaper. That almost always means they are young. We don't discriminate based on age, but if you just looked at the ages of people that we mostly hire then that data would look like we're discriminating based on age when age is not part of the decision at all.