As a prelude to WW2 Hitler annexed Austria and Czechia. This was accomplished without bloodshed, so it was a great strategic victory for the Nazis. In later affairs they were not so lucky however and both war against Poland and later against France cost them substantial losses in men and materials. To add to the wound the undeground forces in occupied countries were constantly harassing and sabotaging them. On the 'bright' side the Nazis could enforce local peoples to work for them and there was plenty of looting too. However it required maintaining a strong occupying force to keep the population in check, a force that could've been used on the warfront otherwise. So here comes my question: did the gains overcome the losses?

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I know that some of Hitlers conquests were carried for strategic/political reasons and did not really help in terms of economics, such as the Balkans or Norway because of their remoteness, rural character and poverty mostly. On the other hand some wealthier countries offered little resistance (Denmark, Benelux countries) and were for sure a nice addition for the Germans. But what about the somewhat developed Poland (at least the west part, especially upper Silesia) and rich France - countries that had something to offer economically but also the ones that resisted greatly? Would the war with them be viable for Hitler for economic reasons only if nothing else?