The highest contrast ratio of the Acer XB270 is 100000000:1. That's over five times the contrast ratio of a 20000000:1 PC screen, which is the most frequently found contrast ratio.
A 100000000:1 dynamic contrast ratio is actually the best contrast ratio amongst all comparable spec PC screens that were released around the same time as the XB270.
The worst contrast ratio across comparable types of flatpanel monitor is Mega Contrast.
We think you might also be interested in some of the other LCD screens that have a 100000000:1 dynamic contrast ratio currently available including because of it's better review score, the Asus PA279 ($749.00).