Probably because that's about what this conflict in Afghanistan and Iraq has cost. In terms of money it's around the cost of the Korea War- of course in terms of loss of life it's no where close: Easily less than 1/10 the combat of combat deaths for US soldiers. And for non US losses: "600,000 Korean soldiers died in the conflict according to US estimates. The total, including all civilians and military soldiers from UN Nations and China, was over 2 million deaths."
http://en.wikipedia.org/wiki/Korean_War
And in terms of population Korea was probably less population than Iraq and Afghanistan [but more population than either Iraq or Aghanistan].
I don't think we have actually spent 250 billion yet but we budgeting for about this much and probably up spending 300 billion or more before these wars are over. We are in addition increasing the miltary budget. During Clinton term miltary spenting was flat or declining in real dollars. Bush is increasing the miltary budget by around 10%. And if you include the cost of wars then it's total of around average of 20% yearly increase. In term of percentage of budget or GNP total Defense spending not particularly high in comparison to yearly average miltary cost during the Cold war period. Of course if the 10 or 20% increase continues for a few more years then we be higher than average- in that case even get up the cost of the Vietnam war.