For SAHMs, what is the monthly household income for you to be comfortable?

When it was just 1-2 children, husband's pay was 1.8k before cpf deduction and our rental cost $138/mth. We lived comfortably. Just have to give up on eating out and fancy food, no cab rides, walk whenevever possible and no shopping for wants. Now husband is bringing home $1.9k/mth, rental is $322/mth excludes bills, 3 kids (no choice have to grab a cab if late due to the chaos kids cause.. lol), we are finding it hard to survive with his pay. So it depends on lifestyle and number of kids. I think for us now, need about $3k/mth at least.