Finman
I don't disagree that it may still be in tanks when you land, however, it is still fuel that you don't need to carry, hence you are spending money unnecessarily.
Using your increased burn figure still gives close on $6 per flight hour extra cost: $6000 per day, $180 000 per month on a 1000 sector day for a single airline.
There is so much fat in the planning already that routinely carrying an extra 300kgs for the wife and kids costs a huge amount of money.
No one disputes the wisdom of carrying extra fuel for perceived contingencies, weather, common delays, notams etc but the prudence of routinely adding excess fuel is what we are discussing.