It's got nothing to do with A, Bor C.
They either charge or they charge even more. Some small fields don't charge, but it usually listed in Pooleys as to the charges.
Some fields will let you do a bunch of T&Gs for a discount, some others give discounts for training flights. Any ways you have to stop and see the man and pay the dosh.
Most places I've been a member of don't charge for home based aircraft, so It's cheaper doing T&Gs there as long as there isn't a NIMBY problem stopping curcuits.
CC