You can't transfer most air miles. Some can be moved around, but not the ones I collect, SIA & KLM.
If you check the normal price for the flight, the breakdown will probably show you taxes as the same as quoted to you, so everyone pays them. That price sounds about right to me as I've just paid about £360 in taxes
I used my SIA air miles twice with American Airlines as they have the cheapest flights, and went to Florida and Vegas on them
