Today I booked 2 tickets:
1 Business Class ticket from AUH to SIN
1 Companion upgrade ticket from AUH to SIN
So after collecting the miles and hoping to get a fair deal; surprise!

The taxes for a Business Class ticket are Dhs 1500 = HKD 750, but the taxes for a companion upgrade are Dhs 3100 = HKD 1600.

More then double the amount of taxes!

Further research shows that one apparently has to pay significantly more fuel surcharge for award tix.
Further devaluation of the AM airmiles