This matches my experiences well. Many of the people I know who are devs in the Bay Area that don't work at Google/FB aren't making more than $80k. The companies pull in grads who couldn't quite make the top companies who don't realize that they will never get a raise or promotion, and many of these people stay for 5-6 years before they realize how hard they are getting screwed.

These companies would NEVER hire an older, experienced developer because they know they wouldn't be able to retain them.

Its worth noting that I work on a dev team where the average age is about 40 (I am 27). We have multiple members of the team nearing retirement. Having the older guys around makes my job much easier and gives me resources that I wouldn't have otherwise. We are able to keep these guys around because we work on interesting projects, don't work more than 40 hours a week, and have a great manager.