There is tons of data being collected on each one of us and it is starting to be aggregated and analyzed. Here are good examples in this article for how that data is being used. A crude way to adjust price based on the buyer on a website is to use a sales funnel with a rules engine that will show upsells/crosssell/downsells based on what the customer has or does not have in their cart. So, if they have put a product in the cart, you do not want to show them an offer during the checkout process for the same product at a cheaper price. This is what I have built and am using in my e-commerce cart.