Based on my limited experience, I think a 16mm symmetrical drop is rare. However based on the picture two things concern me re: this pearl:
- luster: looks only average or below average to me
- surface: doesn't look clean, and typically vendors would provide pic of the cleanest side. So if you set it as a pendant you may still see fairly visible blemishes which may not be ideal
I think color for GSSP is a matter of personal preference so I won't comment on that.
Pricing I'm not sure too as it varies so much based on the color, luster and surface quality. Plus prices of GSSP has gone up quite a bit over the past year.
Do you have more pictures? It'll be good to have different angles and sides to confirm the shape and surface quality. Did the vendor provide any description?
Also, is this from a reputable vendor? For GSSP there is always the risk that the pearl may be dyed.
The new photos show it off much better. It looks great to me! The Pearl Society might help you get an idea of its worth, they have lots of large pearls. Of course that's the retail price, though.