Statistics from our trip (2 people):

Highest cost/gallon fuel - $4.15
Lowest cost/gallon fuel - $3.34
* Note: we use Gas Buddy!

$ 185.89 - total fuel (average gas mileage=23.8mpg)
$ 434.24 - total lodging (average $108.56/night)
$ 488.25 - restaurants (average $97.65/day)
$ 52.00 - admission & tour, Carillon Historical Park (only place that charged)
$. 30.51 - souvenirs
$. 7.24 - ice*, bottled water

* Our cooler is too large to use motel ice to transport our drinks when on the road. In the motel, we use the refrigerator that most mid-range motels provide.

Other things we did:

* In the car was a bag of snacks.
* Brunch is more our style anyway, so we didn't take advantage of the motel breakfast except to get a piece of fruit.
* Get online reservations for a motel in advance. The only problem with this is not knowing what might be closer to our sightseeing gigs, in this type of trip.
* We had to get the tour to Wright's Hawthorn Hill Mansion in advance. They only had tours two days of the week, Wednesdays and Saturdays, twice those days. The earlier tour on Wednesday was already fully booked when we got our tour booked, the week before.