Cranking up the prices is fishy and something to be wary of, but besides that, I think it’s a stretch to call it a scam when it’s not taking any money or rights from you. A bad deal, maybe, if you’re trying to sell your work elsewhere. But I use the app to listen to librivox books I would listen to anyway, and to post previously-published (either in literary journals or posted online) short stories, and fanfiction, none of which I have any real hope of being able to further monetize.
So far, readership is low, but the app hasn’t been around long. It may grow. If it doesn’t, oh well - I can later delete my stories, close my account, and lose nothing. Also, even though there are clearly not many active app users, I personally get more eyes on my work there than on WattPad where my stuff gets no notice among the bazillions of other stories. People actually read and rate my whole book, unlike on WattPad where I have to join a book club to get anyone to read and vote on the first chapter of my book and I attract no attention beyond that. So that in and of itself is something I prefer of Readercoin to WattPad - I can tell how many people read or listened to my work, how many people finished the chapter, the rating on each chapter, etc. obviously if you already have an audience on WattPad or are good at/enjoy the social media style advertising, then WattPad has the advantage, but since I’m not into that I appreciate not having to do it there.
If they were taking money, or had fine print in the TOS demanding rights, or making false promises to attract users, I think it would be fair to call Readercoin a scam. But they’re pretty upfront about what they are. If a hypothetical author with a story that could have otherwise made them big bucks on Kindle or with a trad publisher does Readercoin instead, even that doesn’t mean they were scammed - it just means they didn’t make the best decision, but even then, it’s not too hard to rectify. And for a hobby writer there’s nothing to lose but the time it takes to record and post the story.