True. but having 500K visitors you only need to average $0.01 per visitor to make $5K/month which isn't chump change. If you can average $0.10 per visitor, hire a butler.
This has been my biggest winner, I used to just have categorized information but the minute I started drilling down the content to location my AdSense went thru the roof.
Lots of local service providers are spending good money competing for those referrals compared to more generic offerings.
I still have more general purpose information, things most of you would say are a waste of time, but if you find someone looking you bring them in on a related topic and then upsell them to a higher paying topic they may also be looking for, very similar to upsell in ecommerce sites.
A very popular but lower paying traffic lead-in can earn it's keep easily if people can also find the other topics they seek on your site so your navigation and information exposure is the key.