No one with older kids survives solely on a teachers salary without taking some form of charity or government benefits. Unless they starve their children and live in a hovel.
Also, once you have kids, its a lot harder to be in Kollel. If the mother is working, then you need daycare. If the kids are in real school, you pay tuition.
Anyone who says otherwise is lying. If they have side jobs, they are not living JUST on the teachers salary.