The market sets prices, and the market sets correct prices
not always. Prices are often set on speculation and projection. Take for example, the housing market bubble, Tech bubble, stock market crash of 1929. We don't operate on a pure supply/demand economy. There is a lot more to the modern economy - credit, investment, foreign events, speculation.
Speculation and projection are often what causes demand curves to move. In fact, the 1929 crash was very similar to the tech bubble in the 1990s - even to the point that it was high-tech stocks that led the collapse. Demand for high-yielding stocks far outstripped the supply, causing massive price inflation far above what the stocks were actually worth. Likewise, the housing bubble was caused by an imbalanced supply/demand curve.
You are right that the economy is not entirely supply/demand, but most of what you assume is not supply/demand actually IS, just in a different form. There are only three major forces in the economy: supply, demand, and government regulation. Almost any effect you can see is a direct result of one or more of these forces.
Here's an example: I moved from a rural area to a city, and my car insurance went down by nearly 1/2. It defies market logic, but it fits into a more complicated formula arbitrarily created by the insurance company.
That's not really an arbitrary formula, there's an entire profession based around calculating risks for insurance like that. The odds of your car being involved in an accident are less out in the country compared to in a city, so the insurance rates should reflect this. However, the value of your car, your driving record, age, gender, etc are all invoved in those calculations. More importantly in your case, the distance of your daily commute probably changed enough to lower your rates.