A “developed” pixel contains three colors instead of one. Therefore, a file containing a demosaiced image must be about three times the size of a non-demosaiced (raw) file.
A raw file using 12 bits colordepth is 12 bits per pixel. Assume the demosaiced image is in 8 bits color depth, then that pixel is 24 bits big. Exactly two times. When 16 bits was used then that image will be 48/12=4 times as big.
But one note more. The camera’s raw file is mostly compressed. With my Nikon D750 I can choose between compressed with no quality lose or compressed with quality lose. The D700 had also a not compressed as choose.