You’re absolutely right neither Prince of Persia nor Another World gives off the somewhat amateurish vibe that Jill of the Jungle has. I’m personally not a big Keen fan though, I think I’m enjoying this more actually!
But yeah, $30 seems awfully steep for what it is. I can’t imagine a lot of revenue was generated in Europe. I certainly have never bought one of these old shareware titles, nor have I heard from anyone around me doing so.