You can refine this by adjusting for the miles you would have earned if you paid for the flight. When you buy an airline ticket you are buying transporation plus credit toward future travel. When you redeem miles you receive only transporation.

In your example, if a purchased MKE-DFW-MKE flight would have generated, say, 2,500 miles (including the miles earned by paying with a card), you really redeemed 27,500 rather than 25,000 miles.