Glamgirl, not arguing with you either - and TIP was the reason for my edit actually!
You are right to an extent that this did happen, not least because the profit at LHR was likely to be greater. This all stems from the reality that LGW lost a horrendous amount of money. Some of it was skewed - such as including overheads that weren't remotely fair to LGW (Concorde costs were always a good example) making the figures appear worse than they probably were, but the LGW commercial proposition was always truly grim, and some of the route losses frankly terrifying.