Apologies for the slow and fractured replies, but there are a few simple points which outline this.
If you compare German GDP per capita to that of the UK in 1940, it is 25-33% lower. Further, the grain and crises following the fall of France was quite stark. Though rations were good, Germany was eating into its reserves quite substantially ... This is not a position to be in when you are preparing a land war with Russia.
That isn't strictly true. Pre war, the UK was the world's largest arms exporter, despite having a small Army, it's naval and aircraft industries were both huge and world leading. This allowed Britain to rearm with the latest technologies. In 1941 Britain had started to produce large 4 engine strategic bombers en masse, while the Germans were relying on the nearing obsolete he88 (just as an example). Germany's war effort against Britain was going nowhere, but by mid 1942, Britain's war effort included strategic bombing that would already begin to affect Germany's ability to wage war.
Nonsense?Calling THIS IS ADAM TOOZE CHAPTER 9 ... something nonsense without critically analysing source material is a quick way to a useles discussion.
The simple way to look at this problem was the German was lack of coal and steel. The 4 year plan had already apportioned huge amounts of steel from the civilian sector for the armaments sector, while the munitions production to prepare for France had taken even more. All of this meant that German production in the civilian sector dropped dramatically which in turn had a knock on effect in the German war fighting capability post 1941. While the 'eve' of Barbarossa may be too early as the 'peak Wehrmacht' moment, it had definitely done so by end of that year.
To put it in contrast. Germany of 1936-1940 was spending around 25% of its GDP on the military. This is North Korea levels of economic stupidity.
I'm not sure that Britain is a part of the discussion here. The problem is that once Germany occupied Europe, while it got an initial boost, it was then beholden to provide for those nations. This was worse felt in Coal where Germany suddenly had to make up for British shortfall across all of Europe; it was felt in the steel which was increasingly needed for munitions production. The UK, much derided was either out producing Germany (a larger nation), or simply purchasing the shortfall on the open market. Germany's strength peaked during those summer months of 1941 and it's ability to wage offensive war never reached that capability again (one of the key theses of Frieser's book).