PPX has a bet on whether the doomsday vault designed to hold 4.5 million samples of plant life will be needed in its first year. The seed vault is a bank of biodiversity to counteract the problems of farming moving to a low number of species. If a plant becomes endangered seeds of the plant can be taken from the vault and used to reintroduce the plant. Storing seeds of many varieties means that if conditions devastate one species of plant being grown other similar species with different genes can be used to resist the unfavorable conditions.
The PPX market currently places the chances of the seed vault being used in its first year at 25%. This is a very high probability as if the seed vault is used a serious environmental problem must be underway. The vault is only a final insurance policy against conditions leading to species extinction rather then something for common usage. Imagine you invented a insurance policy that people believed had a ¼ chance of being used in its first year. You would wonder why no one had this policy before?