Clearly you've done this calculation but come up with a different answer. Assuming there is some utility there, it must be the surveillance aspect that is the problem. If you got an Echo, what harm do you think you would likely experience?
If I need peace of mind away from home, I can simply plug in a webcam or connect the otherwise-airgapped security system to the network while I'm away. If I want a hands-free mic, I can buy one with a power switch and connect it to whatever setup I need it for.
If amazon releases hardware that makes it verifiably possible to have such setups, more power to them I suppose. But as likely they won't, as they prefer "all-in-one" solutions that give them "last-mile level" control over how their devices get used, I will probably never buy such devices from them.
I used it a bit, but turned it of permanently after one day I logged in to my router and saw that Echo was generating noticeable amount of traffic even though no one was at home.
I think the only way I could try always on device again is if company like Amazon would provide API and I would create the always-on device.
In short I want to be in control what is being sent and what isn't.
The Echo is a neatly packaged surveillance device that's disguised as a.. What are these things called? Voice assistants?
As with pretty much every IoT device, these things can be broken into by malicious actors and then they get to listen in too. Next thing on the list is that Amazon can do whatever it wants with those recordings and I highly doubt they're only listening in after you mention certain keywords. More likely that's just the trigger to flip the "answer back" switch. And last but not least we should not forget about the surveillance agencies, who will get unrestricted access to this one way or another.
In the grand way of things, this is just another method people are letting themselves being monitored. Just another small step towards total authoritarian control by mega-corporations and dictators. We have to step up and stop this from happening while we still can, or else there won't be any privacy left for anyone of us and the next generation will just grow up with it "being normal".
And before you ask, no, I don't have a smart phone. I have a very dumb phone that I can only use to call someone with or get called myself and more often than not I don't carry it around with me.
The cost here is whatever you can imagine happening if every utterance and the implied judgement of your character escaped into the wild should a keen hacker, nefarious internal actor, or simply a product manager raised by wolves goes ahead "liberates" your data feed. Amazon want to compensate us with, what? ... looks like voice commands and a marginal reduction in search effort, particularly when searching for things they want you to buy from them.
Careful now.