"The retina has a static contrast ratio of around 100:1"
"A higher contrast rating implies a device has greater ability to display black with a deeper shade of black instead of just dark gray with respect to its brightest whites. A home theater projector with a contrast ratio rating of 8,000:1 is more capable of showing a dark subject than one with an 800:1 contrast ratio. But the difference in performance between the two would only become apparent if projection takes place in a completely dark room, one in which is there no light other than that of the projected image.
Equally important is that the eye would not detect a 10 times improvement in contrast performance between these two projectors. Rather, the perceived difference in image performance between these two devices would be just marginal and detectable only if the room is in total darkness.
Marginal, because the eye contrast sensitivity is not linear. While a difference in a contrast ratio of between 10:1 and 20:1 will be definitely distinguishable and a difference between 100:1 and 200:1 as clearly visible, the eye would see the difference between say 400:1 and 800:1 as a minor change. And anything above 1000:1 may not be visible at all.
And it is detectable only in the total absences of ambient light because as we will see further in this article, complete absence of stray light in a room is critical when it comes to contrast performance. This is a rather rare situation in everyday life unless viewing takes place under a controlled environment, such as that of a dedicated home theater with black painted walls."
This fits my experience. I found IPS colors having more impact onto the picture quality than VA contrast, but I can imagine why it is subjective -- after all some people are color blind!