$1 feels like the difference between eating and not eating to some people whereas other people wouldn't stoop to pick a dollar up from the sidewalk if they dropped it.
How "fact-based" do you need this to be?
When you get comparisons in the news about this tax plan or the other, they don't adjust the numbers based on how "$1 feels".
They just use a percent of income - but since low income people pay so little tax in the first place, even a percent reduction looks meager.