It may seem insignificant individually, but 150kgs at todays price of around $1300 tonne is $13*15 = $195 per sector.
Multiply that by, in Ryanair's case alone almost 1000 sectors per day and that's $195 000 per day wasted.
Factor in Easyjet, Baby, BA, Virgin, Jet2 etc and you are looking at hundreds of thousands of $ per day simply discarded.
I may have missed something here but it is that type of perverse mathematics which cause the bean counters and idiot 'managers' to push us ever closer to the edge!
The fuel you put in the tanks
only costs you what is costs to carry it if it is still in the tanks when you land!!!!! = bugger all. That 150 kgs costs 3kgs per hour to carry - thats all. It would cost $195 whether you put it in the tanks at a or b (+/- cost differential).
For those who don't recognize tongue in cheek ....here it comes......you could even put it down to hedging as the price will probably have gone up by the time you land.....so you are actually saving the company money!!