Except we are talking about fuel burn Beagle. Down low all dirtied up we throw around 100kg a minute out the back of the engine. Say we don’t care. On that approach its only say 2-250 kg extra fuel we use. Now multiply that for every approach that aircraft makes in a year. Now multiply that by the entire fleet. Now you get significant extra fuel required to fly your annual program. We had a very bright spark do the cost analysis for us considering all the relevant factors such as engineering costs etc. We even realised that it was worth instigating single engine taxiing after landing. That only saves a cupful at best…but it was still worth it.