I know it's not exactly what you asked, but I booked Y-cabin COS-LAX-NRT-TPE and back for ~$1000 since C-cabin was ~$7K. Just for grins I checked a one-way TPE-NRT-LAX the day befor I departed - and it was $1250 or so in C-cabin!

Of course just the NRT-LAX leg was $5K in C-cabin, so this is yet another example of pricing by route

Richard