Not really. Per the BTS, those two carriers had a combined 5.79% share at DTW. WN's share at MSP is 4.79%. Moreover, the DOT shows that 73.3% of MSP pax are in "low-fare markets", while the comparable number at DTW is 68.8%. Simply put, there isn't much evidence that DTW has an edge in low-fare competition. My guess is that MSP is likely more profitable simply because it is a significantly richer market and that all competitors - low-fare or not - charge more because they can.