Divorce cost

If youve divorced with a child involved, or know someone close to you who did, how much did the divorce cost? Asking NOT for me....someone close to my husband (hes a widower who lost his wife to cancer, somewhat young) is romantically involved with a married woman with 1 son who lives with her husband but claims theyre amicably separated. She has a good job yet claims the only reason she hasnt left him is that divorce is way too expensive. Claims they (she and husband) havent had sex in years. Well this has been going on for about 3 years and she still hasnt left her husband. Our friend who is involved with her truly believes her story of the high divorce cost and wants to help her (which I assume means give her money)....from what I understand, divorce can be done inexpensively especially if theyre as amicable as she claims. He recently put her as a benefactor in his will. I'm worried hes getting taken advantage of and was hoping to tell him that an amicable divorce shouldnt cost tens of thousands. Thanks!