The average German developer works for some non-software low-margin company where he only has limited impact on the business and is treated like a cost center, while the average SF developer works on tech projects with huge margins where he can have a huge impact on the product and is a valued employee.

Because the overall market skews towards lower salaries, even multinationals and the few local tech companies that exist there can pay less in Berlin.

Pay is also generally higher in the US, though usually not to this extent.