According to the USDA, a child born in 2011 will cost an average of $234,900 to raise to age eighteen. If your family makes a salary of more than $100,000 you can raise that number to about $390,000. Yes, there are some savings after the first child — you don’t have to buy another high chair! — but it’s not as though you get a massive volume discount on your subsequent offspring. There are also opportunity costs of a mother’s loss of income from parental leave, scaling back hours or dropping out of the work force entirely. No wonder, according to the USDA, two-parent households with two children devote over one third of their income to their kids. Add it all up and there’s a very strong economic case for stopping at one child.

And yet, the world will tell you — from grandmothers to sitcoms to strangers in the supermarket — that money shouldn’t be a factor in having more children. If you express worry about how much children cost then you’ve clearly got your priorities wrong. You’ll make it work, they tell you. Don’t be selfish.