Which drugs get the most-expensive crown?

If you wonder why Big Pharma is so interested in drugs for rare diseases, here's a possibility: High prices. In fact, a new Forbes survey finds that the cost of meds targeted to small groups of patients with serious genetic disorders dwarfs the prices of drugs for more common maladies, even cancer. The nine most expensive drugs in the world are all rare-disease treatments, it found.

While cancer meds can run into the tens of thousands for a year of treatment, these niche meds can climb to the hundreds of thousands. Witness the most expensive drug in the world, Alexion Pharmaceuticals' Soliris. It's a monoclonal antibody for paroxysymal nocturnal hemoglobinuria, which affects some 8,000 people in the U.S. Price, according to Forbes: $409,500. Three other drugs run more than $350,000 per year.

Another possible reason why this sort of drug is a plus for pharma: insurance reimbursement. Steven Russek, a Medco VP, tells Forbes that he hasn't run across any insurance plans that refuse to pay for rare-disease treatments. They worry whether diagnoses are correct and dosages are calculated properly, yes, but don't say no based on pricing principles.

- read the Forbes story