Okay, but let me raise the counterargument. The Nazi economy of OTL worked, as a looter economy. It let a state with a per capita income below that of Britain punch way out of its weight. And it had a distorted free market, but it was still a freer market than the USSR's.
The problem with a looter economy is that by definition it's outlook is short term. Therefore, it is productive only as long as the conquered areas have something to steal.
The OP never specified how Nazi Germany survives. Let's go with the old 'Britain sues for peace and Hitler dies in May of 1941' as the least implausible scenario. Barbarossa never happens, and the Nazis own Europe. America and Japan comes to blows, and Japan gets squished, so we have a three-way Cold War going on in 1945 - USA/UK, Nazi Germany, and USSR.
Germany has a higher total population, but most of it is occupied. The Germans were never much for administrating conquered areas, and the savage nuttiness of the regime is allowed to prosper under the Goering/Himmler/OKW trioka that replaces Hitler.
Regardless of the larger Geopolitical issues of a three-way Cold War, the Nazi face signficant issues. German companies will have a captive (literally) audience to sell to, but those goods will be increasingly shoddy as German corporations and managemen ossify and stagnate under the joys of slave labor. Production may be high (you can work French/Polish/Balkan slaves literally to death), but there will be no efficiency - especially if slave factories replace prisons.
German leadership was always bewitched by mysticism, so that without a war to distract them, they will give themselves over to their dissapations. Additionally, Sweden, Switzerland will have access to western goods, and some of those will find their way into the Reich. As time goes by, the Reich falls more and more behind, they will have to clamp down to keep those goods out. That will fail, and the Reich will soon face similar issues to that of the USSR.
Mike
What happens now is hard to say.