No, "everyone else" cannot purchase it, because a large portion of the user base never upgraded to Snow Leopard due to the huge range of compatibility problems (see snowleopard.wikidot.com), and the App Store is Snow Leopard only.
That's why The App Store and a whole bunch of other things have been artificially limited to Snow Leopard; they're trying to accumulate enough reasons to force the holdouts to switch -- unfortunately, this mechanism abuses their customers.
The correct path would to have been to ensure compatibility for the huge range of applications and drivers they broke with Snow Leopard. When they chose not to do that, they hard-forked the user base. No, not a typo.
Every iteration has left people behind, this is not news. Several examples on that site that I checked are outdated, so the list's existence isn't a good indication of anything. It's just a wiki, and its last update by anyone was two months ago. One example, the Ableton Live entry, is about 18 months out of date.