The two samples aren't independent, and you can't really isolate other effects (e.g., maybe people buy more in summer for the product at hand?) Secondly, deman

The two samples aren't independent, and you can't really isolate other effects (e.g., maybe people buy more in summer for the product at hand?) Secondly, demand curves in practise aren't that fluid. Plus you want to capture consumer surplus. And and and... Spolsky wrote a post on it once, it has a good and accessible introduction to the concepts, it's called 'Camels and rubber duckies'.