Fast food is one of the main reasons that the Humans of Earth are obese besides the invention of the Internet and Social Networking Sites. If people find that the prices of fast food have increased and fresh food is lower they will be forced depending on their income to get the healthy food. They will be forced to eat and it will become systematic for them to choose the healthy alternative over the fast food.
No, fast food should not cost less than fresh, healthy food, because that is how poorer people end up with poor diets. Even so, the market should control how much things costs. Taxes and other government intervention that inflates the prices of agriculture products should be removed so that fresh food can cost less than fast food.