The pay may not have been that great. How many of the songs that Mat's men sing go on about why would anyone be a soldier risking their lives for poor pay etc. As No 2 in the Companions he would have earned more that most but even in current militaries do generals earn a lot? They probably get more that soneome stacking shelves in some shop but compare them to a top doctor, lawyer, engineer etc.

Not to mention in our world a few hundred years ago officers normally came from rich backgrounds because they needed to be able to read (not a problem here as nearly everyone can read) and they had to be personally wealthy given the lifestyle they were expected to maintain (mess bills, have personal attendants, go to parties if not host them etc)their salery would just about cover the necessities. To a begger on the street their wages might seem high but when you take into account the overheads they might not be too great.