Go look in your junk drawer.
There is a black marker in there. You did not plan to buy it. You cannot remember buying it. You have moved houses with it.
And when you needed to label a box, write on a freezer bag, or sign something for a grandchild, you reached for it without thinking.
That marker is part of a business doing well over a billion dollars a year.
A billion. From a plastic tube of ink that costs about two dollars.
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What makes that remarkable is not the product. It is that dozens of cheaper markers exist, sitting right next to it, and people keep paying more anyway.
The reason why is one of the most useful things you can understand about how prices work.
Here we go.