As well as the first HIB, you can pay as you want. The money you pay goes for the developers, for charity (Electronic Frontier Foundation and/or the Child's Play Charity) and for the HIB itself, you decide how much for each one.
By the time this post was written, they had a revenue of $470,446.62 made in only one day. They have 6 days left to keep making money.
Here is the HIB promo video:
Go and buy it!