UA's code-shares (same experience as MileKing) cost (whenever I check those fares) more than booking the flight with the real carrier - LH/UA flights starting in Switzerland/Austria/Germany being the exception.
Code-shares (even with UA) allow (by booking all flights on one ticket with the 'same' airline) sometimes to profit from a (multi-segment-) one-ticket-price of the same airline (but different carriers).