Originally Posted by Caveat Emperor
I sat down once and did the math. With gas being the way it is (at ~$4 a gallon, between $8-$12 in gas), and assuming I can get a ride to CVG (which I usually can from someone) to save on parking costs ($6 per day in Dayton, $8 per day in Indy), I have to save about $30-40 on a weekend trip to justify flying from Dayton, Columbus or Indy.
It's definitely something you have to consider "real cost" (vs. absolute price on airfare) on when planning.
In the 90's I would fly into Indy and rent a car one way to Cincinnati and drop it off downtown. That's when car rentals were lower and Delta had a tighter hold on the region, I could save $200 easily each time.
Not so much anymore and then as you said you have to factor in the what if I do it that way factor.