I'm not sure what this is supposed to suggest/demonstrate.
Surely you agree that taxing (say) 20% of 60k is different from taxing 20% of 1B. Namely: the former has a much more significant impact on quality-of-life then the latter...
Figuratively speaking, what can you do with 747M that you can't do with 300M?
(Before the pedants inevitably pick this rhetorical question appart: the point is that it's not prima facie unreasonable to tax extreme wealth significantly more heavily than the median income)
Edit: the first of the pedants have arrived... sigh...