Re:
"Some other interesting findings from the study include:

— Only 15-percent always check the weight of a product.
— Only 16-percent always check the unit price.

I am surprised that these numbers are even that high."

If you also include those who OFTEN check the weight/unit price the numbers are even higher - unit price 51% and weight 44%.
However, in Australia for the unit price it is 80%. The higher level is to be expected since provision of unit pricing for packaged products is compulsory for many grocery retailers in Australia whereas in only a few states in the USA.
And consumer awareness of the benefits from comparing unit prices is very high in Australia due to regular consumer education programs.