It is almost exclusively a middle class activity. Also not that expensive if one parent is home. I knew many homeschooled kids who were just given a math textbook and worked through it. You only go to math class in public school for about 182 hours a year, so a diligent kid can do a year of math in a few months no problem.
Rich families already do this by sending their kids to private schools. Have you seen how expensive and competitive these schools are, even starting as early as Kindergarten?
Yes it is. People forget this because they live in a bubble. It’s like remote work, nice for the laptop class, but not possible for the person growing your food and manufacturing your tesla.
We've looking into this, as deeply as we can as "outsiders". We homeschool, but are firmly "middle class" from a national perspective and easily in the top 1% income in our county.
Regardless of income, the key factor seems to be the rationale. If parents want to homeschool because they're involved with their kids' lives and want them to succeed, they'll do well relative to the available public school options.