Though I have never declared an emergency or pan (probably should have a few times in hind sight), I think I'm still missing something here...
If the pilot feels him/herself in a situation such that declaring a pan or emergency is thier best action, would not the landing fee be a very minor consideration, compared to the reassurance of being safely on the ground in a very stressful situation? If you have chosen to land at an airport with more services (probably equates to landing fee amount somehow) you have probably chosen to have those services available. If fire rescue equipment is standing by for you, that's costing money, it's only fair that the user make a contribution toward that cost, in my opinion.
Many people have landed at the runway I own. None have ever been charged, nor offered to pay a landing fee - it's my home, they're welcomed (even the two who have crashed). But, on the other hand, no one has ever offered to cut the grass, blow the snow, fix the ruts they have made, or replace runway lights, when the time comes for that work and cost. (okay, the one pilot who really did crash in a bad way, did come back to help clean up the wreckage)
I won't attempt to defend what are probably rather expensive landing fees in Europe, relative to those charged in Canada, but, paying nothing for having those facilities availabe seems unfair.
For the times in my flying career during which I have been scared stiff, I would have paid a lot to have a runway right there, right then. Generally, there was not one there. Though ultimately it did not cost money to land, I certainly spent a lot longer in peril, and a lot longer worrying about it!
To me, it has similarities to overflying a perfectly suitable fuel stop to save time and landing fees, then worrying the last half hour about your fuel quantity. Pilots, we have enough to worry about already, pay the cost willingly, and land safely!