I think one has to think about how we would like this scenario to play out, in the ideal world. Well, I suppose ideal world, there isn't an earthquake - but let's say that's unavoidable...
...why wouldn't we want to help these people? They are living, breathing human beings, like everyone posting on this forum, that are currently experiencing extreme suffering. The foul, putrid stench of tens of thousands of dead friends and family members, rises from piles of rubble that, a week ago, were the local market or hospital or bar. Hundreds of thousands are on the brink of going hungry, being thirsty, having their health deteriorate. Without sufficient aid this has the potential to turn in to an humanitarian disaster on an unforgettable scale.
The people in Haiti are part of our species, living on our planet, breathing our air. When the children of this earthquake grow up they will be contributing to our society. We are not somehow separate from what is going on there. We live on a tiny island a tiny distance from where the devastation is, and we have the ability and capacity to help.
The long-term positive effects to the entire of global society are far, far greater than any short-term cost of facilitating aid.