The Humble Bundles are actually quite fair on that more than then average. If you jump in early when the average is low you still get the rewards when they drop even if the average has gone higher.
It encourages people like me to pick up the average tier or higher more or less as soon as there is interest.
Or to put it another way, I've bought at least one of these bundles a month for the entire time the humble bundle has been around. It's kind of fun, and when I get a new android device I'm going to have a sea of games my current android can't support to play.