In the discussion about drug costs, the difference in pricing of drugs between Canada and the US was justified on the grounds that US drug companies had to make a high level of profits in the US to support research that could not be supported by the low level of profits made in Canada.

On further thought, it seems that there is a general economic and trade policy problem with holders of de jure (patents, copyrights, etc) and de facto (e.g. 3 companies or fewer with more than 70% of the market?) monopolies or oligopolies. These companies do not use cost-based pricing but instead use profit-maximizing pricing.  In other words, they increase their prices to the point where the next cent in price increase will cause demand to fall enough that their net profits will fall.

In the case of drugs, a global pharma company can implement this profit maximizing strategy independently in each country since non-tariff barriers to trade can be used to prevent the flow of drugs between countries.  This allows global profit maximization, since the willingness to pay may be different between countries based on their economic status and a host of policy and sociological factors. 

Other manufacturers employ the same strategy. The regionalization of DVDs is intended to allow copyright holders to differentially price DVDs in different parts of the world.  Software distributors do the same thing. Even products like cameras are sold at different prices in different countries, although there is a "gray market" of products imported from low-price to high-price areas. The manufactures attempt to dissuade customers from gray market purchases by voiding warranties.

Since many of these companies are American, the general tendency is to rip off the home market and then maximize volume and profit by selling incremental volume above incremental costs in the global market.  This should be stopped by regulation along the following lines:

No company benefiting from de jure or de facto monopoly position may price its product or service to Americans at a price more than 10% above the lowest price charged in any other country, adjusted for the ratio in per capita GDP at the prevailing exchange rates.

Note that this would still let American drug companies charge less for drugs in poor countries, due to the per capita GDP ratio.  However, it would require a rough equalization of prices for drugs sold in the developed countries.