We are in the middle of the peak summer travel season when fares are generally at the their highest. If you are checking for flights in July/August, it should not be any surprise at all that there are few MR options. Prices start going back down again around the last week of August as the kids start going back to school. I see some MSP-DFW-SEA day trip options on AA in Sep/Oct for $250 all-in. Can also do US MSP-PHX-SEA for same price.