[tokenadult]

I've easily spent $5K on self-instructional math materials (which sounds ridiculous, I know

That doesn't sound ridiculous to me, although I don't think I've spent that much on tangible math instruction materials yet for my four homeschooled children. The total budget for my oldest son, including travel expenses to summer math programs and gasoline for travel to local programs, has surely exceeded that by now. I'll open a separate thread

http://news.ycombinator.com/item?id=633540

on the present value of knowing math well, which I have wished to do for a while.