Probably the worst experience I've had along these lines was over paying for bananas at Ft. Lauderdale airport. I can't recall the exact price but it may have been $4 for a banana. At the time it seemed better than hunger (I'd just landed from an international trip).
If there's a logical reason prices are so high in any given situation then it doesn't bother me however in some cases it seems items like the bananas are overpriced just because they can be. I'm a big fan of getting value and quality for the money so when possible I try to prepare ahead of time either with price research or by bringing my own food when going to airports and other high priced places.
An example of this is my recent travels to ostensibly super expensive Oslo. I did pay $20 for a bacon and eggs type breakfast there however most of my meals were much more affordable simply by eating cold meats and cheese from the grocery and then selectively choosing to eat high-quality meals at certain times and places where maximum value (enjoyment could be had). Pingvinen was one of those high-value places to eat (as an aside for travelers to Oslo who might read this).
You make some great points and give some sage advice!