North South
By your logic all aviators should be rich enough to afford massive charges from any airfield. After all, air travel of any kind is so much more expensive than walking.
I have never been in to Battersea - too expensive. I do use the helicopter routes to cross London. The question is, when a pilot has a slight niggling doubt and might land to check, is there a risk that high fees might dissuade him from doing that, and pressing on for the 15 minutes needed to clear the zone to an airfield with more sensible pricing?