Healthcare.gov : really 500 million lines of code?

There have been a number of articles quoting the 500 million LOC (Lines Of Code) that were created for the healthcare.gov web site (e.g., in Slate).

Without getting into the debate about how reliable LOC are as a way of measuring complexity, here's a back-of-the-envelope calculation, including my assumptions.

500,000,000 LOC

Assume 50 LOC of debugged and tested code per day per developer:

10,000,000 "developer-days"

Assume 250 workdays per year:

20,000 "developer-years"

Assume 2 years of development:

10,000 developers

That number seems high to me, even if we include Quality Engineering, Documentation and Management. Or maybe I just don't understand.

Or maybe the 500 million number is really meaningless.