Also, the pizza examples miss out the competition aspect. Pizza restaurants are competing against other pizza places, but also competing against other foods. If someone starts increasing the price and reducing quality of pizzas, then at some point people will start saying "I don't like pizza, let's go for a burger" and eventually a whole generation will grow up thinking that they don't like pizzas as they've only eaten crappy ones.

Ultimately, these kinds of things go in cycles with the population varying between choosing cheap and trashy products and choosing expensive, quality products.