A grocer puts up a sign
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A grocer puts up a sign above his turkeys, "$5 each or $20 for three."
All day long people approach him outraged by his incorrect math, "It should be $15 for three, I'll just buy them separately."
All day people come buy and just buy them separately for less after yelling at him.
After one of his employees watch this go on all day he asks him, "Are you going to fix the sign or what?"
The grocer replies, "What do I need to fix? Before I put up the sign nobody bought three turkeys."