Do carrier-imposed fees fluctuate?

Hi. Do carrier imposed fees ever drop? My planned business class Sydney-London rewards booking through AAdvantage will cost about US$344 (including airport fees) which is much higher than my last long-haul booking (albeit a few years ago). Thanks.

LHR airport recently increased departure taxes in premium cabins.

As the name suggests, it depends whether the carrier or FFP changes their tax/surcharge structures. Currency exchange rates also fluctuates changing the exact cash component amount.

AA and other US-based FFP are known to not pass on carrier surcharges. Hence, the cash component would generally be the government or airport taxes/surcharge only.

Taxes exiting UK are eye watering. Try using land based transport and flying out of other EU ports.