The quip repeated often is that “Marriage is Grand. Divorce is a hundred grand.”
Aside from the financial cost, the emotional cost on all parties can be severe. You are correct in noting that. The question is whether “staying together for the kids” is a good idea or not. And there is no simple answer. Each case is different. Some parents can handle this. Others cannot. Making a decision on this requires doing something that no one can truly do well – predict the future. There is no “One size fits all” here. For one couple, divorce can be the lesser of the evils. For another, staying together with all its challenges might be better. Trying to apply a general answer to this is simply irresponsible. And being blind to negatives of each option is similarly foolish.