> Most people don't buy pasta when rice is expensive.

They would if rice prices went through the roof, which they won't because people who sell rice are not stupid.

Econ 101 certainly explains why you can actually buy gluten free products now (supply for demand) and why gluten free products are usually more expensive (niche market).

My ECON 101 prof talked about the limitations of models and theories based on assumption of rational actors in the 1980s ... I have no idea why everyone thinks this is a gotcha.