All outbound Emirates flights are topping up with fuel bought in UAE, the stuff is probably cheaper than water.
Well, if fuel is cheap in UAE then for Emirates & Etihad only. For everybody else the fuel price there is quite up to the world market, with consideration for less costs on transport and volume.
If you look at Emirates annual accounts, they claim fuel is around 34% within the cost structure, which is about right percentage for any European or US airline. Now the question is whether you really believe Emirates reports?