It's the reverse in a lot of places. It's common in the Baltimore / Washington area to base salaries on years of experience, education level, and industry certifications. I've applied for jobs where the first question HR asks is do you have at least 10 years of experience. These jobs pay as good or better in absolute $ terms than any salary range I've ever seen for engineers in the valley and if you look at it from a cost of living adjusted value the valley pays a lot less.

My two cents is that preferring young employees has a lot to do with the fact that they will work for a lot less money and put up with housing situations that more mature people wouldn't tolerate.