The reality is that coders are systematically underpaid and mostly fungible. The cliche is that you get a raise when you switch jobs (and your new employer knows the least about you). Not that you get a raise when you stay at your old job and differentiate yourself more and more from those other, less competent people who have the same title and qualifications as you, but are somehow worth less to the company.

Coders will never voluntarily allow their salaries to become public. Every coder thinks that he is better than average, and that the salary that he is paid uniquely reflects his superior technical and negotiating abilities. In a misanthropic industry, coders feel that the other employees are their enemy, out to prevent them from being secret ninja superstars.