Gee, Minecraft beta only cost $15 a few years ago, and I'm sure our DS wouldn't care if that was all we ever let him do.
Seriously, though, there are ways to do things cheaply, but it's easier if there are public schools that cater to HG kids. Then the enrichment/etc. is no different than what most parents spend on afterschool activities/sports/camps. I think there is some amount of extra that comes up when you don't have the free decent school available to you, no matter how creative you are. And being creative finding some of the low cost/free alternatives sometimes takes its toll in the amount of time spent. So sometimes it's cheaper to just pay for stuff.
I should say that I had a serious book buying problem when DS was little. I love, love books, and I loved to buy them for DS. When he started tearing through books like candy, we made the switch to the public library. I think most libraries these days have partnerships with other library systems, so if your library doesn't have what you're looking for, you can order it from somewhere else. Very handy. And free.
