A little less than 9 oz less than my pillow. Except I can wake up anytime during the night, from a deep, comfortable sleep, and be alert and function if necessary. And I won't be groggy the next morning.
For me, it's silly to put that junk in my body instead of carrying a bit more weight for a comfortable bed. Just as it's silly to eat cold food instead of carrying a stove. Backpack hunting is hard enough as it is. I have no desire to make it harder or less comfortable. The little luxuries of a comfortable bed, hot food, and a steaming cup of coffee in the morning are all part of an excellent hunting experience.
I guess that's what some time in the military did for me. Cold food, no problem. No coffee, no big deal. No pillow, no issues. I can take sleep aids and they dont make me groggy or affect my function. But I do forget sometimes how that stuff works on other people. My wife is an example, nighttime cold medicine puts her out like a coma patient for 4 hours and she wakes up with a hangover.