Apologies, I have been away with work so slightly off grid! Thanks for your responses, it's helpful in understanding I was right in thinking the number may be high.

I am unsure whether it helps but our routing is DUB-LHR-AUS-JFK-LHR-BCN with the JFK-LHR leg being Jan 2023. Could this by the reason why there's a higher than expected price quoted? Is there an impact if the upgraded leg isn't a straight return? I have done this type of upgrade before with different US entry/exit albeit with same start/end EU points and the price wasn't nearly this high!