The cheapest round trip flights from MCI to DCA for any dates in the next six months were priced from about $230 - $260 and from about $230 - $260 (nonstop). A few lucky people found prices as low as $210.
The best day to depart a roundtrip ticket from Kansas City to Washington, D.C. is Monday, saving $20. The best day to return is Monday, saving up to $20.