Thanks. Yes the fare difference is indeed ~$4k.
Can I assume the mileage upgrade (if there is) will cost a lot of miles since the fare difference is lots of money?
For TPAC flights the recent mileage upgrade awards from PE (which your G fare indicates) to D1 have cost 45,000 SkyMiles; that’s in one direction, not round trip. That’s what I was quoted in December for a MSP-HND-MSP trip. The flights to Asia seem to be quite full, plus DMs with GUCs take precedence over mileage awards for the upgrades. You have to call to ask about availability.
I was waitlisted for the upgrades in both direction but did not get upgraded.