Originally Posted by AmD950

So my answer is still valid.
You can upgrade with cash but not with miles.

FYI: https://www.cathaypacific.com/cx/en_...omy-fares.html

Are redemption and bookable upgrades available for all Economy fare types?No, redemption upgrades and bookable upgrade vouchers are available for Essential and Flex fares only.

Are airport and inflight cash upgrades available to all fare types?Yes, eligibility for airport and inflight cash upgrades remains the same, and is available to all fare types.

Originally Posted by AmD950

If you are on 160 stock cash ticket (and the agent decided to help you), you need to pay the price difference between your business class ticket and first class ticket.
For CX548, usually at HK$10,000-HK$15,000 difference.