Medication is a commodity like oil or corn futures, not a product like a toaster. The price on some medications fluxuates daily. The flu vaccine is a really good example of one where price is all over the board depending on things like international demand (for a specific regional outbreak), and domestic demand at the beginning of winter, and even output changes at manufacturing facilities. In oregon distributors are limited somewhat on profit margin which is the reason fred meyer has to price match on anything in their current stock. There's also something about fred meyer being incorporated in california since they sold the company, argh I'm too tired to remember all of it.

Dad trades in pharmaceuticals and has tried to explain it to me on a couple of times.