Well I have a perm hearing damage after having done 700 hours without ANR.
I find it makes me less tired.
I am able to turn the volume down on the radios.
I don't get tinitus
Now I think I got my pair o DC10 for 350 quid which i got the VAt back on through the school and also got a tax rebate as well while applying for my Proffessional pilots tax code thingy. So all in the cost me about 200 quid or as at the time 20 hours of instructing.
Now that set has done me for 4000 hours so in Captial costs its at 5p an hour and decreasing.
So including batterys call it 20p.
You can't put a price on your hearing. They do work, they do reduce the damage. Its very easy to get a student to purchase a pair of ANR DC's I just lend them my spare pair (which i have cause the aircraft spares are rank) then after a couple of lessons forget to bring them. Usually it comes up quite quickly in the debrief the question "where is the cheapest place to get a pair of them DC's"
Ther daft thing is if you get more than 5 of you together you can get a bulk discount from suppliers.