Do you fly that route regularly?

Instead of buying a one way ICN-SFO, you can buy a R/T for $450 more.

Now you have an SFO-ICN R ticket for $450, and for ICN-SFO buy the inexpensive one way or another round trip ticket leaving you with another cheap outbound for future use.

I do this with JFK-BKK and save $1000+ by buying r/t tickets originating in BKK and using the JFK-BKK for a future trip.

This is ICN-SFO October 5-19 but is pretty similar across a wide range of dates.