President Obama’s soaring speech on Friday announcing the drawdown and eventual pullout of troops from Iraq, framed by martial music and the cheering of an audience of Marines when he gave the timetable, could not help but be seen partly in an economic frame of reference: The war has cost an estimated $860 billion; Mr. Obama, as a candidate last year, repeatedly criticized such spending overseas during a downturn; and he had just unveiled his 10-year budget plan the day before.