Upgrading Fare Buckets - Cost Help

Good afternoon,
I booked a flight to the States for 2 passengers flying out on Sat Aug 29th on VS21 and returning on Sat Sept 5th on VS10. I paid £944 each which included £483 of ‘fees.’ This was for an M outbound, X return and the difference in tax to upgrade to upper on the outbound leg. I’m now looking to upgrade the inbound leg to an M so I’m able to initially upgrade to PE but eventually UC when they’re available.
I’ve just spoken to the FC and they say it will cost £346.50 per passenger to change the inbound fare code and that doesn’t include the difference in taxes per cabin. I thought this sounded like quite a lot… Is my maths below correct?!
My ticket, out G, return X: £944 (£483 fees)
Difference in Y and J tax & fees on outbound leg: £124
Therefore, ticket price for M out and X back was roughly: £820
Current return price in M: £908
So… surely, to upgrade my inbound to an M fare should be £88? Or at least, thereabouts and no where near the £346.50 per passenger.
As a side note, I can upgrade to a K fare for £75 and then possibly upgrade with my FlyingCo miles?
Thanks for any insight!
Mike
I booked a flight to the States for 2 passengers flying out on Sat Aug 29th on VS21 and returning on Sat Sept 5th on VS10. I paid £944 each which included £483 of ‘fees.’ This was for an M outbound, X return and the difference in tax to upgrade to upper on the outbound leg. I’m now looking to upgrade the inbound leg to an M so I’m able to initially upgrade to PE but eventually UC when they’re available.
I’ve just spoken to the FC and they say it will cost £346.50 per passenger to change the inbound fare code and that doesn’t include the difference in taxes per cabin. I thought this sounded like quite a lot… Is my maths below correct?!
My ticket, out G, return X: £944 (£483 fees)
Difference in Y and J tax & fees on outbound leg: £124
Therefore, ticket price for M out and X back was roughly: £820
Current return price in M: £908
So… surely, to upgrade my inbound to an M fare should be £88? Or at least, thereabouts and no where near the £346.50 per passenger.
As a side note, I can upgrade to a K fare for £75 and then possibly upgrade with my FlyingCo miles?
Thanks for any insight!
Mike