Originally Posted by
pandaperth
The difference is dramatic in your cases, which to me implies that CX (the first carrier in your 2nd itinerary) is more zealous in collecting surcharges for other carriers than is IB (the first carrier in your 1st itinerary)...
I think it's the other way around - IB and Qantas are notorious surcharge collectors; CX isn't.
The additional continents will also add to the taxes/fees total, not to mention the base price.