I am looking for the best TTS out there for FreePBX.
I have heard that putting Google TTS is kind of a “hack” and should not be done.
Is there an easy way to get a really good working TTS?
In my opinion, IBM Watson TTS, but is kind of a "hack"too 
Easy to implement
the “BEST” are going to be commercial
The “Second Best” will likely be through unintended or unofficial API’s (such as google, I have not looked at Watson I think that has an official API)
Then you have something like flite which is included. I think someone is getting ready to submit a patch for Watson…
Watson: https://www.ibm.com/watson/developercloud/text-to-speech.html#pricing-block First million characters free
AWS Polly: https://aws.amazon.com/polly/pricing/ 5 Million characters free for 12 months. Then $4 per million after
For reference ~23hrs per million characters