It was a somewhat-arbitrary line. $60k/yr is about $3k/mo takehome. While that's not a lot of money, it's enough to live a modest lifestyle including a mortgage and raising children with only a single parent working. I'm not saying it won't be a struggle, but it's doable. It's how I was raised and it's how most of my family lives, and I'm in NJ, which is in the top 10 most expensive states. My niece and nephew-in-law live comfortably on $70k with two kids, two cars, one earner, and just bought a house. Life is hard and that's ok.