Originally Posted by
FewMiles
It's not so much of an upgrade as an "upfare" -- you can pay the fare difference to the next higher class of service. So starting from a deeper discount fare, you'd have to pay more.
Currently a one-way Business Class SFO-HKG is at $4017 (C-class). Assuming the op had a low-ball fare (which I would assume between $800-900), I still don't know how CX calculated the figure $1700.