If extra fuel is taken but not burnt, who the he'll cares. The remaining fuel would mean the next fuel load to be added will be less, thus not "costing" more money.
It ain't rocket science!!
Rocket
Sorry mate, but you're wrong.
When we are talking tonnes of fuel, it burns fuel to tanker fuel.
Think if you carry 7 tones extra, that could translate into the equivalent weight of roughly 70 pax.
Obviously the more fuel you carry, the more fuel you burn carrying it!
I always like to have a minimum of half an hour of fuel in the tanks excluding reserves regardless when I arrive. There is nothing worse than watching the fuel gauge and recalculating your fuel constantly second guessing yourself. As Murphy usually has it, the day you go minimum fuel is the day you're held, or given huge track miles, or slowed down to a crawl at a low level.
I like to have a bit of fat for my own sanity!