O.F.;
Cost should never trump safety.
No, it shouldn't.
But it does, mainly because most of the time such a decision is made (commercial versus safety priorities) the circumstances are complex, there are many factors pulling the decision-makers in both directions and on any one day, it is possible, given history, experience, competency, either decision could be, in the moment, the correct one.
I know of at least three A320 heavy landings which exceeded the certification limits in which the airplane flew again, right away. I know at least one was a commercial decision until Airbus got hold of the data and grounded the airplane. Often it isn't nearly as clear-cut and airlines have significant challenges today with horribly low fares and therefore precious little money with which to "do the right thing". The industry is so far retaining its enviable safety record and that says something about successful decision-making and cost-cutting. But the phrase, "Fine-tuning the Odds Until Something Breaks", was the title of a paper written by William Starbuck on the Challenger accident. Great title, great point. And Diane Vaughn has written a superb book entitled, "The Challenger Launch Decision" - an excellent examination of the organizational culture and the "normalization of deviance" at NASA which led to the first, and many agree, the second shuttle.
I think the same thing applies today and it takes awareness of these factors and strong leadership to cut costs at an airline and remain as safe as possible. It isn't black-and-white.