"The simple answer is because they can. European governments control prices in various ways—Britain has the strictest system, refusing to pay for medicines that fail to meet a threshold of cost-effectiveness. But in America companies set whatever official price they like."
If anyone's interested, England's system of health technology assessment (HTA) for the NHS is extremely transparent and world-leading. It's one of the things that we Brits should be extremely proud of (although pharma-sponsored sob story campaigns in tabloid newspapers may suggest otherwise). All new technologies are investigated in terms of incremental quality of life gain (vs current treatment norms) and changes in…
NIHCE's greatest contribution has been that, in insisting on being evidence-based as de-politicised any and all questions about what treatments should be available.
I think this week's US shenanigans have showed that de-politicising healthcare is a very laudable goal.