Kevin Costner's Ex-Wife, Here's Why She Lost Big in Divorce

Kevin Costner's ex-wife may have screwed herself in their epic divorce, all because she listed everything under the sun as an expense she'd need covered in almost a quarter of a million dollars in monthly child support ... even though her final amount ended up being far, far less.

TMZ has a new documentary about this uncoupling -- one of the most acrimonious we've seen in a long time here in Hollywood -- and a particular element about the proceeding that was fascinating is the fact that Christine shot for the moon in what she was seeking at first.

Of course, we're referring to the $248k in monthly child support she wanted from Kevin -- an astronomical amount that she justified with an absurd list of expenses she said she needed.

Among those costs she said she needed covered ... cosmetic surgeries, and other luxuries -- like boutique shopping, massive ATM withdrawals, and sky-high attorney's fees.

In the end ... a judge gave her a fraction of what she wanted -- even though Kevin offered her more than she ended up getting.

We talked to lots of folks in the know about celebrity divorces to see why they thought Christine swung for the fences ... and we got some interesting insights. Turns out there's really no such thing as an iron-clad prenup.

The doc gets into all of this and more -- "TMZ Investigates: Kevin Costner's Divorce War" is a deep dive into the nasty split, examining how it devolved into a war over money, cheating allegations, and entitlement.