Today, it takes nearly 2x the median household income to get something resembling that kind of life. Granted, you're still considered middle class at that level of income...
I think you are off of what you intended by an order of magnitude on that house size. (And a bit high for reality even after correcting for that error.)
Tangentially related: https://www.census.gov/const/C25Ann/sftotalmedavgsqft.pdf
I don't think it's too high, though. My parents built something on the order of 5,000 sqft in the early 70's for around $15,000 (including the 5 acres of land), adjusted for inflation that's under $150,000. My Mom was able to put herself through 4 years of college by waiting tables part time.
Yeah, we had it good. Why? My dad's blue collar job burying and splicing telephone lines for Ma'Bell.
It really was a different time. That same job today comes with no job security and remarkably similar wages as it was 40 years ago, even as the cost of living and inflation has increased tenfold.
In some cities. In other cities, that's just not true. Example: in Atlanta, GA, the median income is right over $55k. According to Zillow, that will get you a house in the $227k range. There are tons of single-family houses with yards in that price range (or even half that) in the city.
I ran similar math for Dallas, TX. I'd bet there are a lot of markets where this is true.
Housing is only expensive in the expensive housing markets.
Zillow and other home pushers are interested in selling houses, not in the consequences for the buyers thereafter.
All that said, in Atlanta, 3 BR/2 BA houses are abundant in the under-$150k range. Or under $100k. It's really not approaching necessary to earn 2x the median income in cities like Atlanta to buy a house with a yard.
The point is the OP's math assumes one lives in a high-cost area, which is not the reality where most Americans live.
$1.8k housing, plus $500 for property taxes and insurance, $1,000 for two vehicles (payments, insurance (damned teenage drivers), gas, maintenance), $500 into savings for household emergencies, $800 to feed four, $100 per person for clothing, the occasional ice cream, paying off medical deductables... and you're quickly looking at needing over $5,000 a month gross just to get by.
5,000 / 0.7 * 12 = $85,000
Toss in 10% savings and 10% retirement, and you're well over $100,000.
Sure, you can cut corners and live off a lot less than that, but I'm comparing it to the standard of living had by people 40 years ago.
(Random nitpick: if you're earning the median income, paying a mortgage while contributing to retirement; and have 2 kids, you are not paying anything close to 30% of your income in income taxes.)
Also you are right that if you save ~30% of your median income ($500 + 10% savings + 10% retirement), the month-to-month gets a little tighter. But then you can retire early. :-)
I'm not arguing that everything is roses, just that tens of millions of people live at the median income and own houses, cars, etc.
You'd have done much better here arguing about the costs of childcare or higher education. Those are a bloodbath, no matter where you are.