Even Jeffrey Sachs--whose numbers on the effect of increased "openness" on economic growth are in my opinion way, way high--would only claim that $1 in increased ability to export generates $5 of increased economic product.
East Germany's total exports in the mid-1980s were, IIRC, about 5% of GDP less than one would expect if it had been a "normal" capitalist country. Applying the Sachs 5-for-1 rule would then suggest that had trade been at "normal" levels East German GDP would have been not one-quarter but a little less than one-third that of West Germany...
Brad DeLong