So far, I haven’t self published, so I have nothing with KU. But some authors I know have put work out via KU, because it is good for exposure. KU readers will often purchase works from authors they first found on KU for free. However, Amazon uses pages read as a method of calculating payment, and there have been issues. One issue I’d heard about some time ago was that a feature Amazon added, to allow readers to fast forward or skip back in a book, caused the page read count to be shown as one page. Not great if you get paid by the page… That may or may not have been fixed.
But what I did hear recently via Twitter was that Amazon allocates payment from a total pool of revenue, based on pages read. (I do not know if this is limited to indie authors, but I would assume so, since no publisher would want this deal.) In any event, some authors reported being paid as little as $0.004 a page. Given how much it can cost for cover art, editing, proofreading, and formatting, when a three hundred page book earns you $1.20 per reader/sale, it’s going to take a good long time to recoup your outlay and make any profit at all.