I think on QF ticketed, the QF surcharge may depend on the point of origin. My very first one was ex-TYO QF plated, and I had SYD-DFW on QF with no noticeable surcharges on the ticket. ex-TYO (well ex-Japan) tends to be minimal across the board (though not zero). Similarly on an ex-Japan CX plated the year after, I had AKL-DFW, AA operated, QF coded with no extra surcharges.

I suspect on (potentially) high surcharge points of origin like OSL or what CAI used to be, it would have been far more variable. Then you have to be a lot more cognizant of plating carrier and / or marketing carrier.