I think I concur with your findings. Certain airlines, when you go directly to their websites, will ask if your dates are flexible. I believe both Delta and West Jet have grids where you can align departure and return dates that present the varying costs based on the specific day of the week. My experience has been Tuesdays and Wednesdays are typically lower, but exceptions do exist. In reality this only makes sense because business people will typically fly on Mondays and Fridays, while many tourists fly weekend to weekend. That would leave a void regarding the middle of the week. This is just one more step in the battle to find 'reasonable' air prices!