I think you have to include Tales of the Unexpected as well. It followed a similar trajectory as Mystery in Space - sci-fi/fantasy anthology and then features sci-fi hero (Adam Strange/Space Ranger).
I can't see how you'll see much more than the steady growth bc mentioned - I mean, with the big explosions in price for PCH and GGA, and then too the oddball superhero stuff like Ace, and never mind the usual grail books, especially in grade... How much money can there be in our hobby??? It does seem to concentrate itself in some of those areas, and so be it: we still need some (relative) bargains somewhere!