So much depends on your area, what "normal" conditions tend to be, and the quality of your avg. diver. I can see some places calling a blow out in seas and weather that others would call a good day.
I have been on a few trips where the capt. kept looking back to see if we were going to call the dive, you see in the North East if the boat gets off the dock and the capt turns back, the ride was free, if the passengers call the dive, we pay. There is also not discount if you only get in one dive on a two dive trip.
I have also been out where were start discribing the seas a One Pill, Two Pills, or the whole bottle.
But there was one time out with Cape Ann Divers in Cape Ann, MA where we had paid for a wreck dive and the weather by even my standards sucked. The boat went out in rain, fog, high winds, with thunder and lighting in the area. We ended up at Foly's Cove where most usualy shore dive. I was pissed to say the least and have never been back on that shops boats and have no problem in naming the shop.