Marketing and the brand play a big part.
How about natural vs. synthetics?
Montale is famous for his "rose" scents. It literally requires a ton of roses in order to get a few quarts of essense/oils. If you were to use synthetics, you can bypass this process and mix chemicals/aromatics together. You should post this question on the Health section. We do have a few knowledgeable fragrance experts on the forum.