It's all up to the individual person. Some people only consider it a true run if it's under 2 cents per mile; others are happy with 4 or even higher.
Everyone here probably has a different definition of what constitutes the "right" value of a mileage run for them.
For example, I think 146$ coast-to-coast is a great deal, (say about 6000 miles roundtrip), but other people here may disagree. There's no set number