Stricly from a loss of life, you're correct. However, you're over simplifying the nature of Afganistan (and Iraq). This is a protracted war with no end in sight, unlike Normandy. We don't get to storm the some beach or secure the hilltop - rather, we have no idea what the outcome will be. In essence, the loss of any U.S. life now is costlier, as we will likely see no return.

In fact, one might argue after all is said and done, the U.S. (and western world) will be less safe once we pull out of this region, as we have destroyed all their infrastructure and created a haven for radical militant groups.