In '73 a Chevy Nova just under $2500, which CPI is just under $20k. Median household income was around $12k

$25k is about right for a cheap new car today (you can get a few base models for less than that, but good luck finding one). Median household income is around $83k. So a cheap new car cost went up by 10x but income only went up by less than 5x. Inflation implies it should cost 8x as much, but it costs 10x as much.

Of course the Chevy Nova didn't have ABS, airbags, a touch screen, an automatic transmission, power steering, or retractable seat belts. Car companies could make models without some of these (though most are required by law; can't even have a car without a screen since RVC is mandated). But now they would be competing with used cars that have most, if not all, of these things and cost less.