Andrew is right. There is big difference btw business school and econ/mgt school, and there is big difference between acc/fin and econ.
Plus, 30w is not a lot at all !!! you need to consider how much time and effort we put in to get a phd degree. In US, an acc/fin AP can earn double of 30w (after tax) in a PURE teaching school. i know this as i have quite a number of friends there.