Are these numbers inflation adjusted? The difference would be far more dramatic if not.
I think they are inflation-adjusted. Here's an inflation-adjusted source that explicitly lets you pick FY2021 dollars as the reference:
https://aerospace.csis.org/data/space-launch-to-low-earth-or...
It puts the Saturn V at $5k USD/kg, the same as this article.
What's interesting is that it shows a general downward trend a little more clearly than this one does, but the Falcon 9 and Falcon Heavy are still very shocking outliers.
https://reference.wolfram.com/language/ref/InflationAdjust.h...
https://docs.google.com/spreadsheets/u/0/d/1TPewJ64QNVtM5sbR...
There's a column there for inflation-adjusted prices, but not much data in it.
Edit looks like it was updated minutes ago