It's like anything else, the common/less in demand notes get discounted.
The tougher prefixes/grades get full book or even premiums.
The $100 notes were highly saved by non-collectors, grandpas and so on, usually not in unc though.
Inversely, high denoms are collected les, so the value in relation to face is less..
I',m not sure the catalog should show an increase in the notes that are always discounted.
They should probably leave them the same for a year, and just increase the ones that are hot or rarely seen.