The good news may not continue indefinitely, but the total cost of the first year of the Medicare prescription drug benefit was nearly 30% less than projected, according to an Associated Press analysis of data from the Centers for Medicare & Medicaid Services. The total tab was $30 billion in 2006.

Lower-than-expected enrollment and a lower-than-expected rise in drug prices before the benefit started are two key factors responsible for the lower cost of the benefit, the data showed. The price tag of the Medicare Part D program was projected to be $43 billion.

CMS has lowered its projected cost for the drug benefit through 2015 to $729 billion, which is almost $200 billion below the original estimate, the AP found.