Credit card numbers have dropped precipitously in value in recent years as PHI replaces it on the underground market. Why? Cyber criminals use the PHI to engage in medical fraud which, because of its complexity, may continue undetected for years. Theft and misuse of credit cards, on the other hand, is usually detected almost immediately and the cards canceled. In addition, in part because the financial industry has had many more years to develop sturdy safeguards against data theft, healthcare industry data is relatively easier for thieves to access.
See Reuters article at “Your medical record is worth more to hackers than your credit card”