Well, I did add this at the end - the question of corruption , the amount we give in aid that never goes to the end we wanted it to - but for now, I am asking about the actual cost in terms of world GDP.
Turns out lower than I though. here is another site with better figures.

http://www.globalissues.org/article/26/poverty-facts-and-stats

scroll down and you get an itemised bill in Billions, not trillions.