I'm finding this one a little hard to swallow.
I understand. I did too the first time I saw that idea posited. A historian (forget the name, I'll try to post it later) did some research on the governmental budgets of the imperial powers from the 1890's up to the Great War. Most of the commercial enterprises in European colonies (depending on the country) were either tolerated monopolies or gov't franchises, and this historian could actually track governmental and business investment vs. actual returns. Probably didn't get all the cash flows, but he thinks he got most of them. The Belgians came the closest to making Congo pay for itself, but only through incredibly brutal enslavement of the population that created an outcry so loud the King was forced to give up control of the colony to the Parliament. The French, Brits, Germans and Italians all spent more on infrastructure, construction, capital imports, etc. in their colonies than they got out of them through extraction of primary commodities. In fact, various British governments (especially Gladstone) opposed imperial expansion because it was so expensive (among other reasons). Bismark actually gave a speech in the Reichstag indicating that colonies were economic nonsense - only after he was kicked out of office did the Krauts get into the land grab big time.
Kind of runs counter to everything we've been told for years, doesn't it? Also pokes some sizeable holes in Lenin's theory of the First World War - that it was inevitable based on the desperate search by capitalists for new colonial markets. In 1914 Germany exported twice as much to Belgium as it did to all its colonies put together...