check base cost responsivity wrt default airports
base cost sensitivity seems to be different for default airports
#1 Updated by planetmaker about 7 years ago
av8 has a NewGRF parameter which can control introduction dates and costs of a few (default) airports. This can be highly confusing...
Maybe it could be mimmiced on this side (though it rather should be taken care of by av8)
See Pikka's explanation further down the thread linked earlier