I've just discovered how people find and sell used balls
I played my round today and for some reason had the nastiest push slice from start to finish with my driver. I'm talking about landing past the cut, past the rough, past the rougher rough, and into the overgrowth.
I lost 7 balls, and managed to find and punch out the rest. But in the course of doing so, I found 34 balls just today in those no go zones alone without much digging around - and there were far FAR more I could have taken. They were all within 10 feet of each other as well, just heaps of mis hit balls.
So if you're ever on the hunt for used balls, just look where the slicers/pushes would land their drives