Great question. While there's no stock answer, let's take a look at what the Illinois Secretary of State has to say on the subject.
Click on the image and you can get a look at the Secretary of State's math. According to the Jessie White's office, the "average" cost of a DUI conviction in Illinois is over $16,100.
We regularly do quite a bit better than this for our clients, especially when our representation results in dismissal of the charges.
This chart anticipates hiring an attorney "uncontested plea" - meaning walk in and give up, we suppose. But whatever we might think of the Secretary's assumptions and calculations, that's one hefty price-tag!
For an independent take on the structure of anticipated attorney fees for DUI, check out this take on DUIAttorney.com.