As an extension to this, I had an itinerary CAI-xCMN-JFK-DCA-DFW-MEL-xSYD-(SIN-MLE)-xDOH-SEZ-xDOH-LHR-DOH which I've asked to be changed to:
CAI-xCMN-JFK-DCA-DFW-MEL-xSYD-SIN-xCMB-MLE-xDOH-SEZ-DOH-LHR-IST-AMM which I was told was valid and sent off for pricing.
Now they've come back they want ~£740pp including the ~£101 change fee.
Question is - does this sound right? Calculating the added taxes via ITA Matrix for IST-AMM comes to about £100pp and SIN-xCMB-MLE about £60pp. I haven't done LHR-IST but considering I had already paid APD for LHR-DOH I can't imagine it being a lot more.
Additionally this is before the first segment, so I'm expecting a reprice but looking at EF I can see the DONE5 fare CAI-CAI filed on 26/12/23 is the same price I had paid originally (or very very close, the 145k EGP translates to ~£20 or so difference via Google rate).
In total including change fees I'd expect somewhere around £600 or less for 2 rather than the £1400 they want. I did indeed call AA RTW desk and spent 40 minutes on hold where they said they were on the phone with pricing but they ended up hanging up on me

Calling back they said they would raise it with pricing and I should call back tomorrow.
What's my best course of action here? Or am I really missing something that will make it cost that much?
Thank you all for the continued advice
Edit: by my own calculations of the changed segments I found that this change would have been £1 or so due to reduction of YQ DOH-LHR and APD from £191 to £26 however after pressing with AA they are certain it's correct so I've had to pay it anyway.
That said, I have the fare tax calculation figures, can anyone make more sense of it than me?
Old ticket:
Fare : EGP 145000.00
Taxes : 521.70 YQ 309.60 YR 47.50 XT
Fare Calculation: CAISEZDOHLONDOH4785.47NUC4785.47END ROE30.30 XT41.10YR4.70AY1.70PZXFDFW4.5PD191.00GB55.81UB10.9 0EG4.10XK20.90QH1.40JK1.70EQ19.70MA35.40US5.50YC5. 90XY3.20XA9.40AY33.40AU8.80QR3.60WG31.90WY50.20BQ5 0.20H927.60QA.80PZ27.60G441.80DW.40O2.80O94.60R91. 70S412.5
New ticket:
Fare : EGP 145000.00
Taxes : 722.20 YQ 350.70 YR 678.90 XT
Fare Calculation 0NUC0END ROE30.30XT304.30YQ255.70YR41.20ZZ27.00SG6.70L75.00 OP17.80TR2.70M62.10O712.60P13.80XFDFW4.5PD14.10AY2 .50PZ26.00GB55.81UB10.90EG4.10XK20.90QH1.40JK1.70E Q19.70MA35.40US5.50YC5.90XY3.20XA33.40AU8.80QR50.2 0BQ50.20H927.60QA27.60G441.80DW.40O2.80O94.6
Is there any way I can estimate the taxes using ITA to calculate on 001 stock?
Additionally, am I correct in the total ticket value should be the fare + the taxes? At 145000EGP (~3778GBP), £720.2 YQ, 350.7 YR, 678.9 XT that comes to £5527.8 pp however my credit card charges (there has been multiple due to them saying there is technical limitations with EGP) comes to £6258.61 which is more than what it says?
Would appreciate anyone's advice again on this because if I've overpaid £629.81pp taking into account the change fee I would very much like it back.