Hard quantitative data on MSF seems difficult to come by so these estimates a going to be very rough. We will approach the problem in two ways.
First MSF reports having 100k patients on life saving anti-retroviral therapy. And for 2006 their budget was $560m. If we estimate this represents 2-10% of their achievements this puts the total economic value of their achievements at $90-450b for a 150-800 Leverage Factor.
Second they report having 2,000 international and 25,000 national staff. Based on this if we estimate they have 5,000 doctors, and each doctor saves a life every 1 day to 2 weeks this puts the total economic value of their achievements at $250b-2.5t for a 400-4,000 Leverage Factor.
The truth probably lies somewhere between these two estimates.
250 - 2,000