I am the developer of the app Speech Central, one of the leading text-to-speech apps in terms of features, user satisfaction, growth and overall usage. Starting from August 1st 2021 the app is completely free for the blind people without any hidden cost.
There is no trick, my revenues from other users are enough to support the ongoing development of the app and I have decided to help to those in need. I believe that the app meets or exceeds the features of other leading text-to-speech apps and I'll be glad to hear opinions and suggestions for the new features and improvements.
You can get the app from the App Store using this link: https://apps.apple.com/us/app/speech-central-voice-reader/id1127349155 and if you are using VoiceOver the app will detect it and won't ask you for any purchase.
P.S. at the moment the app exists for the macOS too, but as it is a paid app it is not possible to detect whether the user uses some assistive technology before the purchase and as such it is technically impossible to make it free for the blind users only.