I used math academy for several months. I was curious and wanted to try it out since it’s a problem I’ve also worked on in the past. Th system is good, the fractional spaced repetition is a nice system and really reduces the spaced repetition overhead. Still IMHO, it provides nowhere near the value of the $50 a month pricing. But again I also know a lot of higher level mathematics and can work my way through a topology book on my own, so I’m probably not in the target audience. Still, I would think that even for people wanting to get into math or high school students this would still be a very steep price.