I buy 15-20 DCA-DTW tickets a year and while prices have increased somewhat, they have not gone up dramatically for advance purchase tickets. Years past I would typically pay 119-139 for a K fare with 14-21 day advance purchase requirement. Now these same tickets are 179-199 most of the time. One thing I have noticed is that Delta dramatically increased their last minute fares. For as long as I can remember, you could buy a ticket a day or so before departure for mid 300's in Q, now it looks like the cheapest is nearly 800 in M. It also looks like Delta has put a Saturday night stay requirement, so now that blows up a ticket to mid 400's.