I think a good number do. Prior to the "donation arrangement", there was a set amount of money that you had to pay to get anything you picked up at the literature counter. I know many dubs who never made a big deal out of getting money from those they left the magazines with, even when the price was printed right on them.
Somewhere in the 80's (after Jimmy Swaggert had a lawsuit brought against his ministry) the Society abuptly stopped printing a price on the mags and suddenly we were merely to donate what we thought the Bibles, books, magazines and tapes we ordered were worth. From that point on, I think the WTS started having some difficulties with expenses. It was all too easy to skip throwing money into the box for things. All dubs had to go on was if they'd ordered something in the past and what that cost them at the time. Very few wanted to put in what such items would go for in the retail world. I think it was hard to remember to facter in inflation, etc...
At any rate, I always "paid" something for the magazines because I didn't feel like asking for donations from people out in service. I suppose you could handle it any way you wanted to really.