IME, limited as it is, when I have compared one-way ticket pricing (cash) to round-trip pricing on OZ or KE, there were no bargains. If I had 80K miles to burn, I'd consider an off-peak Economy round-trip, or an off-peak one-way in Business. IIRC, one leg of an off-peak Economy ticket is 35K miles, and one leg of an off-peak Business ticket is 62.5K miles. I'd pay cash for Economy if I couldn't find a good redemption.

Last time we took the whole famn damily to Korea (four of us), we did peak Economy LAX to ICN, and off-peak Business ICN to LAX to save miles. Mrs. Zippy has also gone off-peak Business, LAX to ICN on OZ, and off-peak Business ICN to LAX on KE. But that was partially funded by Chase UR points.