Earlier quoted context omitted.
A complex tango between drug companies that want to maintain their margins, and European governments that want to drive drug prices artificially low to force American payers to make up the difference.
You're getting downvoted, but you're right. Currently, the US is implicitly subsidizing other countries in this regard. If we removed the trade barriers for prescription drugs, US prices would fall and other countries would end up paying more.
Seriously, if drug companies were making a net loss in European and other countries, they'd just stop supplying in those countries and subsequently enjoy higher profits. Unless you're suggesting companies like Pfizer and Merck & Co do it anyway out of the goodness of their hearts. And prices the US pay are in no way related to what other countries pay: it's simply a function of market power and being in a much weaker bargaining position.
Most of these countries have 'single buyers': essentially a panel of medical practitioners and economists who negotiate prices on the basis of cost-benefit ratio on behalf of the entire country. So the lower drug prices in European countries (and other single buyer/universal insurance countries like Britain, Australia, Canada etc.) is simply drug companies supplying the market at the price it will bear. They are price takers in such countries, because those countries are monoponsy markets.
I realise Pfizer (net income: $7.74 billion) and Merck & Co (net income: $4.44 billion) are really doing it tough, but I think they'll be OK if Americans realise it's insane to pay close to double (>15%) the OECD average (7-8%, medical spending as a % of GDP). Although I hear US medical treatment is top notch if you're rich, otherwise statistically (and conservatively) 25% of the time it will send you bankrupt, assuming you make it out of the waiting room alive (compared to, say, the UK where medical costs account for %5 of households that report 'financial difficulty'). [0]
It truly baffles me when I hear Americans talk about this issue, as they always argue it's actually really a good thing that they're getting rogered by most of the private medical industry in their country (hey, they're nice people, we cuddle afterwards). There's some crazy mental gymnastics going on if you truly believe that paying double the 'rich country club' average on health care costs for basically the same outcomes (apart from the much higher bankruptcy rate) is in some way a good thing.
It's almost like some weird form of buyers' remorse: 'Yeah, but we treat cancer better that anyone. USA #1!'
[0] http://www.snopes.com/643000-bankruptcies-in-the-u-s-every-y...