I'm not so sure about this, I believe it was stated that SW was in the range of 80k in sales, do we know if that is yearly or monthly? Seems way to high to be monthly. If it's yearly, her commission wouldn't likely be more than 50% (I'm being conservative here), so maybe she was making 40k annually. If I'm wrong and that is a monthly figure, she would have been making a lot of money. If she was, I think it's less likely that money was a factor in motive as she could have had to pay him alimony.
Edited: quoted wrong person. Sorry.