@picofarad usually amazon polly or elevenlabs, these days. coqui also has a commercial offering of xtts.

you can apparently get some good mileage out of xtts and rvc if you are willing/able to make your own fine tunes. i haven't because my rig with the big AMD card still doesn't have a working linux though. i use piper-tts to read long articles to me or make one-shot audiobooks.