We always find cheaper rates flying South West out of Flint instead of Detroit. Would that be an option for you?
I just booked our July trip on New Years eve and was able to get tickets for about 180 round trip per person. For us, that's the lowest we've seen in the last few years.
I absolutely love flying out of Flint instead of Detroit. The airport is less hectic and no where near as gigantic. Everyone that I know who has flown out of Flint has stayed clear of Metro when given the chance after.