normaluser_

It sounds like you are an upper middle or upper class family. There are gifted children in the US that aren't identified as such that come from lower class families who are deprived of their education. I checked the AoPs site and if you get the pre-algebra -> calculus textbooks + solution guides it's over $200. This may not sound like a lot to you (as you suggested) because it is due to your class. This is something some poor families cannot do. Even if they want to buy those books. Sending your middle schooler or high schooler to take college level classes is another sign of class status. I believe we should have schools like AoPs and the Proof School targeted not at the wealthy gifted children, but poor gifted children. I also think these schools shouldn't filter applicants out by SAT scores (since mostly gifted children from well off families seem to do better than gifted children without access to education). It seems like most places ignorantly assume the gifted only come from well-off places and put cultural barriers (such as exams) to identify them. This class advantage carries over into university admissions when the well-off students have 30-60+ credit hours from colleges coming in, as opposed to the gifted kids from poor families with 0 college credits. The former are admitted to elite schools, while the latter are denied. If you look around, these elite prep schools and elite colleges tend to lack economic diversity. Teaching advance math to gifted children of the elite, while excluding the gifted children of the poor (due to barriers of entry) do a disservice to our society as a whole.