How much a PhD is worth- the price of a PhD in the usability profession

Does a PhD pay off financially? The author recently helped conduct the statistical analysis of the UPA 2009 salary survey, and used this opportunity to look into the data to see if he could calculate how much a PhD affects salaries in this profession. The data set contained salary information for a wide range of jobs in the profession—usability engineers, designers, managers and information architects.

How much a PhD is worth- the price of a PhD in the usability profession