No, I don't think it is normal.
I started watching President's week '04 fares from DTW in earnest mid-summer. I ended up buying flights on Spirit for around $200 pp RT direct in September, and the flights went down in price briefly (and with better times) mid-december.
NWA briefly matched that price sometime during the late fall, though not on such good times, but generally was between $50 and $100 higher per person for comparable flights.
Based on what I'm seeing this spring, summer, and early fall, I don't expect to get a deal quite that good again this year. NWA is running a southeast fare sale, and even with that none of their fares are under $225 except tuesday/wednesday-only roundtrips. So, for weekend travel in February '06 from DTW, I'll immediately buy anything under $225 this year, and I won't feel taken advantage of as long as I'm paying less than $275 or even $300 pp.