I believe most airports charge landing fee's based on the tonnage of an aircraft e.g. £10 per tonne. Therefore the bigger the aircraft, the higher the charge. The landing fee can/normally includes a set period of free parking as well. After that parking charges are applicable.
Airports also put various charges on the airlines for passengers. Normally a set charge per passenger, with a lower charge for domestic pax.
I believe the min charge for NEMA is £30 + VAT.