There is a lot of support for students who can’t afford to take the test. What isn’t really included is test prep. China has the gaokao, which everyone can take, but the prep factor is real even if they tried to outlaw it.
(Yes, it takes time and commitment but it's mostly not the case that paying for test prep courses automatically translates into higher scores.)
And yes, money helps a lot to brute force what material works for a kid and get motivated teachers. It's not a magic bullet, but it's a lot better than no bullet.
Education is free and freely available.
"Maximize your score with free Official Digital SAT® Prep"