Iron Man #1 numbers are the ones I used in the OP, but it's seemingly the same among most SA keys, despite different pyramids of quantity on the census.
I know, it's even worse with Moderns, because a 9.8 may fetch $200 and the 9.6 might only go for $40.
There are smaller differences in price between 8.5 and 9.0 despite being much different in grade (mostly). 9.4 to 9.6 is the matter of a very small defect. It's insanity.
9.8 I can usually understand, since it's the most-common near-Gem grade. It's kinda the 'gold standard'. The drops from there are monstrous.