Comparative pearl sizes-- how much difference does 1mm larger really make?

I've imported and resold pearls since 1965. I was never much interested in the growing details beyond what my jeweler customers could easily understand in a sales presentation. I've had this question a few times and if I had the insight to present this information, if I had it, it would have made my, explanation much better assuming they knew about the volume of a sphere.
This is fantastic and useful information! Wish I had it in my "radar" the last time I gave a pearl sales education course. Thank you very much for sharing :D