I recall a survey done one time: The cost of raising a child to the age of 18 is like 100K. That does not include things like sports, braces, University, a car at 16.
It is the "basic" expenses, so when Darlie saw the two boys she saw them as expenses that were always going to be expenses. She saw them as "using up" the megre family resources.
So it may not have been the insurance money directly, but since they did bury them in one casket and one plot, the cost of burial would be half.
But any future money that the family would have would only have to put towards two adults and one child(who is a lot less expensive then older children)so in essence they cut their family expenses quite a bit with the murder. Supporting one child who is a baby, is a lot different then supporting 2 older kids and one baby. Now you have reduced your dependents by 2/3.
By the way, anyone is capable of anything for what ever reason that they seems to "justify" it in their mind.
Nothing surprises me anyone, really nothing. Not the mother who pours bleach down her daughters throat, who stabs her kids, who shoots or smothers her kids, who scalds her kids, who "sells" your daughter, who "invites" a man to "visit" her daughter bedroom, who gives their kids drugs, who has their kids sell drugs for them, to leaving a new born in a trash container, who lights a house fire and tells the kids not to leave their room, to a parents who lockkids up in cages. To people who beat a child into a coma.
Really nothing surprises me anymore. It is not a stretch that Darlie killed her kids. Unfortunately, parents, Dad's and mothers have done a lot worse. Darlie should have been therapy, actually both her and Hubby, maybe that might have saved the kids lives.