Every year I come to the S.C.A's annual Pensic War and sell my stuffed plague rats.
I have learned that the person who comes to Pensic with $5 over what he needs for food etc. will not buy a rat. The person who comes with $50 may buy a rat. The person who comes with $100 will buy a rat. The person who comes with $500 will buy a rat and may buy 2 or 3. (One guy buys a bunch for his jack russell terriers.) The person who comes with $5000 will buy no more rats than the peson with $500, and may buy fewer, as he brought money for a high ticket item.

I call this Ratenomics.