There are usually two approaches – programs which usually charge fees, but with some exceptions, and programs which usually don’t charge fees, with some exceptions.
Velocity *used* to be in the no or low fee camp – but with recent changes is more in the adding fees side, unfortunately.
Qantas is in the add fees camp, but with some exceptions – see American Airlines and Fiji Airways (low, but not no, fees).
KrisFlyer charges fuel surcharges on it’s own flights but most of it’s Star Alliance partner flights are low charges, but with a more expensive award chart.
Asia Miles generally imposes surcharges but they can be a bit lower than some other oneworld airlines.
US frequent flyer programs generally don’t impose charges but for flights on some airlines they do.
Simple eh 🙂
Pretty much every award program charges taxes, but the amount varies significantly. Some airlines add on large fuel charges, particularly British Airways. Singapore and Qantas also have quite expensive taxes. Another factor is individual country airport taxes. For example, any long haul business flights leaving the UK will automatically have another $300-400 added on top in departure tax. Some countries such as Brazil and the Philippines have banned taxes and surcharges. The amount of taxes charged for a particular airline can also change significantly depending on which program’s points you are using. Finally, some airlines have relatively low fees, such as AA (other than with BA), Lifemiles and Aeroplan.
Basically the answer is that taxes and fees vary for a wide range of reasons, so it’s hard to say definitively.