The international community cannot tolerate genocide, or a nation crumpling under the tyrannical will of a brutal warlord. Intervention in Darfur is within the scope of the power of the UN, and any costs incurred by such an intervention are more than offset by the savings of human suffering in the region. Allowing a region like Darfur to remain in a perpetual state of war and unrest damages other nations in the region, which has a ripple effect to the entire world.
The international community cannot allow a genocide to happen in Darfur. The local forces of the Sudanese government are poorly equipped, and a Western intervention could easily subdue them. If a foreign country wanted to pay a small price, they could have signigicant effects a protecting the refugees in Darfur.