Seen in a Stanford cafeteria last week:

A sign that said

Donut holes
2 for 25 cents
6 for $1.00

But fortunately the cafeteria was not in the Economics Department.
By the way, after I mentioned this to the people behind the counter, they changed the sign — it was now 2 for 30 cents, 7 for $1.00. That makes somewhat more sense. (Though what baked goods are ever normally sold in 7s? Is it a baker’s half dozen?) Yet it seemed like a shame: A member of the public noticed an error, and the result is that the rest of the public now has to pay more. There oughtta be a law, I tell ya . . . .