This discussion gets me every single time. All three of my younger sisters are stay at home moms and their husbands make less than I do, and they have kids, whereas I don't. Until you're at least a deca-millionaire, no amount of money will ever feel like enough and you'll be stressed, or at least I will be, and I'm sure my sisters are, but the material differences in our day to day lives are nil. Their houses are smaller and they live in the middle of nowhere, whereas I live downtown in a major metro, but I also barely leave the house, so what difference does it make?
Everybody who thinks they absolutely cannot do it needs to take a long hard look in the mirror and ask how it is that 7 billion or so other people manage it with even less. It's nice not ever worrying about bills or paying much attention to what anything costs, but it's not that nice. I'm not actually any happier now than when I was living with four guys in a two bed apartment in the slums of Long Beach.
In my anecdotal experience the trend seems to be the less well-off families have stay-at-home moms, while the well-off professionals both work. It largely seems that the "no one can afford kids" idea is an excuse to not give up the DINK life style or at least dual income.