Airport Taxes

[realestate]

Although booking 12 months ahead using points, I could not find a through flight from Frankfurt to Sydney in J but was able to book Franfurt to Singapore on QF6 some weeks ago and I have now been lucky enough to grab the final leg Singapore to Sydney on QF6 also to connect with the first leg booked previously.
I note the tax Frankfurt to Singapore is $353 after conversion from Euros and the tax Singapore to Sydney is $237 after conversion from Singapore dollars.
As I am now transiting only through Singapore, I asked Qantas to adjust the Taxes as I understand a direct flight is always less tax than having a stopover and there may be other savings that I am not aware of.
However Qantas says that because I have 2 booking numbers, I have to wear the full taxes.
Does that mean Qantas will pocket the Singapore departure tax at the very least and there may well be other savings for them?
As I don't really understand how these taxes are calculated, others may have some comments one way or the other.:evil:

 

[JohnK]

I guess some part of it may well be a Singapore departure tax.

Looking at direct booking FRA-SYD and the taxes are 366.22EUR. Not sure what conversion rate you used for your comparison. Now I believe this would include a YQ charge (fuel surcharge) for Europe-Australia.

If you have 2 bookings FRA-SIN and SIN-SYD then you will be hit with 2 YQ charges, one for Europe-Singapore and one for Singapore-Australia which will be more than the single Europe-Australia YQ charge.