As above, it's totally dependant on the frame in question. As an example though, my large 5.7C frame weighed about 110g more than the medium.
Unless otherwise specified, frame weight claims by manufacturers are typically for small frames, and probably often the lightest example they have weighed.
If you want real numbers, try googling for people who have independently weighed their own frames. There's a lot of info out there if you look hard enough.