David & I always fly into Detroit since we are in the British Airways frequent flyer thing, prefer non-stop flights, and Detroit has a non-stop service that's convenient for our family as far as picking-up & dropping-off goes. Brother lives in Toledo about an hour away.
Our flights to Detroit last July were £1000 for both of us.
Our flights to Detroit this November will be £540 for both of us.
We book our flights direectly with BA, since we get more airmiles for it. Other than that, we use Expedia and have had fabulous results with them.
It's been more expensive, every time we've looked, to fly into Chicago and drive to the Detroit area. Also, driving in Chicago is a b*tch, and the Detroit airport could not be ANY easier to find or get out of (in my opinion) - so it's a lot less stress for us. You can still get flights cheaper to Chicago, but it's never by much, and by the time you rent the car, apy the tolls etc - it comes out even anyway. The flight into Chicago is nicer, it's a bigger plane, but that's the only incentive as far as David & I are concerned, so we don't use Chicago at all anymore.
We've also considered flying into other areas, in Ohio, in New York etc - and iether catching another flight or driving... but again, when we've ast down and really figured out all the costs, it's wasn't enough of a savings to justify the hassle of it all.
Hope that helps.