Cheap migrant labor from the communist side offset the German economy for a period of time, and in North Korea the cheap labor would be several times the amount that of East Germany. Secondly, the economic differences between the two Germanys were less than that of the two Koreas. Thirdly, East Germany used to interact with foreign nations to some degree with international economic exchanges. North Korea on the other hand is totally isolated from the rest of the world. Still today East Germany is far behind its West counterpart in terms of economic development.
The North today is still very strict about maintaining its policy. It has learned the weaknesses of East Germany and has done everything possible to ensure such an event won't happen. Presently, no North Koreans are allowed to step outside the country boundaries. No foreign influence is allowed, and the people live on whatever lies and cheats their government gives them. North Koreans, according to "A Panorama of 5000 Years: Korean History", have very little knowledge of the outside world. They are told that the South has betrayed the Koreans by accepting American support and influence, and thus the South needs to be "liberated". This in my opinion is rather surprising; the South has been able to hold on to its culture and traditions from the past few millenniums, while the North outlaws not only foreign influence, but also any of its own traditional or cultural elements. According to a North Korean news service, "News from Korean Central News Agency of DPRK", the US has colonized S. Korea, committing war crimes and robbing the nation since 1945. It claims "the total amount of human and material damage the U.S. imperialists have inflicted upon the South Korean people for nearly 60 years since their occupation of South Korea runs into 43,139,020,630,000 U.S. dollars.".
As one can see from the above, the two Koreas have become vastly different, and the government sides see each other with confusion and misunderstanding.