As a younger developer I certainly had an unrealistic idea of my value to the company's profitability which has attenuated to a more realistic assessment these days: maybe that's part of why "older developers" are satisfied with relatively lower salaries. It may also be to do with a healthy attitude to work/life balance: demanding a higher salary can correlate with greater demands on your time (including even weekend work).
My view is that competent developers can rise to the level of income they deserve, without sweating it too much that others with more experience are somehow keeping them back.
