Earlier quoted context omitted.
That statistic seems slightly off to me. If we assume that the breasts are the same density as water (which is probably too high, as they're mostly fat, which is less dense than water), 23 pounds is about equal to a 12 inch by 7.5 inch by 7.5 inch block of pure flesh. Maybe it's just me, but I think that fails a simple sanity test. Edit: Wikipedia says "The average breast weighs about 0.5 kilograms (1.1 lb)" with som…
"D-cup" also isn't enough information to gauge volume. A 36-D is larger than a 34-D. And remember that volume (and hence mass) increases as the cube of length, so two inches more in length will mean a lot more mass.
FWIW: Cup size is an increase in circumference, not length. And cup size is a relative measure. A "D" cup is supposed to mean that the fullest part of the breast is 4 inches more than the ribcage in circumference. So a 34D is going to be much less mass than a 44D (but, ironically, also a lot "fuller" looking relative to the rest of her figure). The last statistics I heard: The average American woman is about 5'4" tall and a size 16 dress size. More girth around the ribcage due to weight means "average" cup sizes that equal more mass because cup size is very much relative to that initial ribcage measurement. (I'm reminded that not long ago there was an article posted on HN apparently about women getting both shorter and fatter on average -- or so I gathered from the comments.)