Oh, there's one more little detail:
Doctors choose the more expensive drug more than half a million times every year, a choice that costs the Medicare program, the largest single customer, an extra $1 billion or more annually.
Jonathan Chait sums up:
The story explains how Genentech has outmaneuvered the federal government, preventing it from requiring Medicare to reimburse Avastin instead. The reasons for this vast waste of taxpayer money are at once boring and infuriating, but they boil down to rules preventing the federal government from managing its Medicare dollars wisely.