"a necessity"

Nothing can compete against an artwork of 2-3 million polygons made by an talented artist. The only way to realize such art in everyday life is with displacement (and other) maps. You can try to recreate with 200000 polygons until the day you die, but you will never get even near.

A far better way to compare would be to show two renders of a highpoly (2-3MB) masterpiece. One say with 50000 polys and the other with 200000 polys. In both case with displacement (and other) maps made by an expert.

Then we could vote if the quality improvement was worth the extra time and cost which of course could be used instead to other quality enhancing labor.