Certainly appears to be salvagable. Usually when a K bike sits, it's the fuel system that suffers most. Fortunately, they have an aluminum fuel tank, so that should be OK. The internals, like the fuel pump, pump holder, filter and probably all of the internal fuel lines will need replacing. Could be about $300-400 in parts alone. Then there is the injectors. They may just need cleaning.
The other big "if", is the ABS, which on these BMW's are notorious for not operating, and are expensive to fix.

This is my old 1990, non ABS K75S.