OTOH, if you know or suspect that astroturfing has a very low ROI, you have lots of motivation to not publish anything, but instead tell the clients: "our ROI is spectacular, but unfortunately we can't show any data or stats because you know, we have to do it in secret, so just trust us and pay us $TONS_OF_MONEY, and it'll all be awesome!"
Try this yourself - use imgur and upload some reaction gifs to an account so you can go back and see the view count later.
Don't spam the images but work your way through some comments sections from /all, find some comments you can use your reaction gif on and head back to imgur a few hours later. I expect you may be surprised just how many views that one link you posted got.
Comments get way more views than a picture because people will read a comment more often as they scroll past than people who click a link.
Now imagine you're someone who wants to promote an idea or a product. The amount of eyes that go over what you type into that comment box has the power to drive big traffic. Even just a few thousand views from one comment looking at or even just thinking about that product or idea on a large scale with barely any effort.
I can't prove it happens but I'm more than confident it does.
Is there any actual evidence of this as a widespread phenomenon? The /r/hailcorporate people are among the most annoying on Reddit.