Bingo. Greed is a universal human constant and therefore a poor explanation for differences.
Drug development costs are enormous, partly because of the nature of the game and partly because of government regulations (This is not an argument against all regulations, but let's not kid ourselves that the regulations are cost free.) Many experimental drugs don't pan out. So when a winner comes along, the drug company has to set the price so as to recover: production set-up costs, the marginal cost of producing each pill (or whatever), the development costs of the drug being sold, and a share of the development costs of all the failed experimental drugs.
Because we still have vestige of a free market even in health care in this country, the drug companies mostly can recover the above costs. But other countries insist on lower prices. Because they're recovering all the above costs in the US, the drug companies can afford to sell to other countries at anything above the marginal cost of production. That's why drug prices are cheaper elsewhere.
So the other countries are free riding on our functioning system, just as they free ride on our defense expenditures. If we import US drugs from other countries, we'll be trying to free ride on ourselves. Only a Democrat would believe that's possible.