The Story

There's a difference between a "doll" and a "toy".

A "doll" is a figure which represents a human, and any company which imports a "doll" to the US is charged a 12% tax

A "toy" is essentially (in this context) a figurine that can represent anything non-human (robot, dinosaur etc.)

Any company which imports a "toy" to the US is charged a 6.8% tax.

This is why it was beneficial for Marvel to claim that Mutants weren't humans, essentially to not be taxed so much on figurine imports.