Is it more expensive to fly London - LA and return San Francisco-London?

Generally, flying from London to Los Angeles and returning from San Francisco to London can be more expensive than a round-trip flight between London and Los Angeles. This is because multi-city itineraries often incur additional costs due to the complexity of the routing, and airlines may charge higher fares for one-way segments compared to round trips. However, prices can vary based on factors like the time of booking, seasonality, and specific airlines, so it's best to compare fares for both options to determine which is more economical for your travel dates.