According to this article, the salaries of Linux system administrators has increased by 50% in recent times. What level of skill do you need to be considered a professional Linux administrator? and what was the original salary level? If it was only 20,000 per year, that isn't much of an increase.
http://www.linuxtoday.com/it_management ... 701735NWBZ
Edit- sorry this is a better link: http://www.linux-foundation.org/weblogs ... -rises-50/