Many airlines no longer co pair the back end with the front end as flight attendants and pilots have different rules governing how much they can work. It is better from the airline's point of view to maximize the productivity of each work group rather than working both to the lowest common denominator, and the sums are large at the end of the month.
As for the cost of having an accident. That is why airlines have insurance. I hate to say it, but its just a balance sheet item to management and as long as they don't run too many of them together in too short a span and thereby attract regulatory interest its no big deal to them. The public doesn't care either. They shop based on price and convienience.
Cheers
Wino