Much SAT prep is free. The study materials are ubiquitous.

The SAT is also incredibly easy. I got a 1200/1600 when I was in the 6th grade while going to a inner city school. I wasn't exactly doing SAT prep then.

high school and public libraries have ton of _absolutely_free_ materials for SAT prep, this is really lame excuse.

it is not the lack of money that is holding the kids, it is lack of willpower to push yourself to top 10%/1%/0.1%.

It is hard work and not every kid can do it, considering all the leisure alternatives they got

Money==High SAT is silly meme that only lazy parents perpetuate. If money could give high SAT then there would be no need in Legacy Admissions in the first place! (Why need legacy backdoor, if you can hire tutor to get top 0.1% score?)

Most schools now offer free prep classes, and every school library (and public library) has more study materials than you could ever need.

You can't improve that much on the SAT. Anyone can buy the online test prep courses and study them. They aren't going to turn a knuckle dragger into a genius, they're just going to maximize an individual within their band and remove the penalties for lack of familiarity with the test context.