Humble Bundle is a quite recent marketing idea. You come up with a set of items and allow people to pay what they want for those items. It sounds open to abuse, and it is. People will always pay as little as they can unless the people they’re paying have built up the kind of rare loyalty that earns them a tip.
Where Humble Bundles genius shows is in its bonuses. If you pay the minimum amount then you’ll only get the very basic tier of items (which was coincidentally the only ones I didn’t own), but if you pay a premium price then there are premium items that will be added to your order, and that are still a bargain to buy at those prices. Then there’s the third tier of items that is available to anyone who pays more than the average price people are paying, making it a nice midway point between paying the minimum and shelling out the full amount.
At the moment there is a Humble Bundle available for ebooks of my beloved Transformers franchise. Pay the minimum (which ended up being less than a pound for me) and you get issues 1 through 50 of the original Marvel Comics Transformers series which ran for 80 issues (this is the US run and not the largely superior UK run). The average price nets you the 21 issue All Hail Megatron IDW jumping on point story, 5 issues of Transformers: Spotlight, the brilliant 12 issue Autocracy storyline and more currently unannounced comics (as the average price on Humble Bundles increase, so do the things that are included in them). Finally, the premium price point adds Volumes 1 and 2 of the two ongoing series More Than Meets The Eye and Robots In Disguise into the bargain.
If giant robots are your thing (and if not why not?) then you need to head on over there right now.