I get these feelings of purpose when I see numbers that increase with sets or groups.
For example, this morning I was looking at the pricing structure of this game development platform/framework called Moai. They have tiers of price packs which include, among other things, the number of API calls included with each level.
They go from a free tier of 100,000 to a paid tier one step up that increases to 2,000,000. Something about these numbers and this jump reminds me of the time I spent playing EverQuest.
I like progressive numbers.