Exactly. There is no cost model that accounts for the device constantly streaming realtime audio data to Amazon. Just doesn't make sense.

But it could still record background audio and transmit it later to Amazon, when an Alexa query is triggered. How do we know that it doesn't do that? Has anyone opened up the data stream to check what audio it contains?

You can measure the amount of data it's sending so you can at least verify it's not uploading vastly more audio than expected.

They could do sneaky stuff like upload the audio after the wake word + a few seconds BEFORE the wake word. The cost benefit of this doesn't seem high especially if you consider that Amazon says all the time that they want to 'earn customer trust'.

Maybe they have hundreds of secret wake words triggering recording and covert upload of audio. It's not hard to implement - they already have 3 wake words, and ability to record audio locally. A list of national security words and marketing words would be the first choices that pop into my mind.

Do you trust them not to waste this opportunity to get more user info? What about future software updates and especially user targeted software updates? They could avoid detection by only doing surveillance on selected targets. When they are caught, they can justify it with some "improving services" or "software bug" bullshit excuse.

> doing natural language processing on the resulting audio recording is what must be offloaded to Amazon, as it's too computationally heavy to perform that process locally.

This is an unquestioned assumption actually.

I think it's way more to do with the NLP system being very very proprietary.

I wouldn't be surprised if it could be done locally, computing is pretty powerful, but they never bothered to even try and make it work locally. Because "cloud computing" is a dream come true for businesses, hiding their special sauce, not having to explain what they're doing (whether it's hard or not) and always maintain control.