Actually, I can see reason behind this. Basically what he said is "Okay, but you have to pay for it, so I don't appear weak at home". When compared to other presidents, Trump has been a peacenik so far. Telling the iraqis something like "Yeah, we'll leave your shitty region, just pay us a few billions" sounds as if the iraqis could get the money by crowdfunding via the internet. The 23 billions somewhere mentioned also are less than 10% of their annual GDP, and can probably payed off as deferred payment. If much of the region wants the US gone, that's actually a very small price.