How is this cheaper than Google TTS? Google's standard voices are $4 per million characters. And the deep learning ones are $16 per million characters, same as this offering. Plus Google gives you the first 1M free every month.
Once you scale to ~60M characters per month, it's 50% cheaper. In other words, if you're at a stage where you spend $1,000/mo on text-to-speech, you'd spend $500/mo instead.
This service might be cheaper than Google at scale, but if I needed 60M chars a month I’d probably care about those features.