Costs of the Afghanistan War, in Lives and Dollars (usnews.com)

By withdrawing from Afghanistan in a way that handed it back to the Taliban on a silver platter, all of those costs (in particular the lost lives of American soldiers) were in vain.

Any US withdrawal was going to end with the Taliban taking over, regardless of method. All of the costs were always going to be in vain as there was no way to actually win.