For people looking for a free alternative (free for Apple users)

Thanks for pointing this out. Fwiw we do hope to continue providing a useful free tier with users, I appreciate your comment because it leverages services that iOS/macOS users reliably have for free by virtue of being an Apple user

Apple's Siri voices are actually really good! (Better than Speechify voices)

This is really interesting - particularly because Speechify makes a pretty substantial amount of revenue from paid subscriptions. I imagine that Apple has the resources and capability to continue to improve their voice quality