whilst I don't disagree that some BAA income is gained from parking charges Northside, it is very much more from fare paying passengers and the additional money they spend in the main Terminal so that's where the focus is. And anyway, no parking revenue is gained from those aircraft that park on Harrod's or Inflite's ramp areas - and that tends to be most of them.
BTW - anyone noticed the new terminal extension is partly open now landside - no arriving passengers coming through that area yet until the end of June, but you can use the new loos and see how much bigger it will be. And I believe Immigration are putting in some new automated desks that will mean you can go through without queueing with everyone else. Maybe.