Does anyone know of a plugin that allows me to raise the price as more people buy something on my site? The first ten to buy through Paypal get it free, the next ten for $50, the next ten for $100, and so on. Kind of like some of the WSO's here and how the price rises as more people purchase. Is there a plugin I could use for this on my site? I just can't think of the right keywords to search for.