Matthew Yglesias asks this question of members of Congress who vote for deficit-funded war appropriations but vote against any domestic programs that raise the deficit:

Is the performance of a Provincial Reconstruction Team in Khost Province more important to the long-term interests of American citizens than the performance of the Riverside County Public Schools?

The question becomes more pointed when you factor in the odds of success of each project. Given the same expenditure, the odds of stabilizing Afghanistan are very low while the odds of improving schools are very high.