I think the potential user base is pretty big. If the power consumption is so low that you can basically not recognize it on your monthly bill, then it would basically be a free nerd lottery where you can just simply run it forever and hope to hit a block.

Do you have any estimates how much such a device would cost to produce and what it would finally cost to sell so it makes sense for you?

I think if you can have such a device for under 100 USD then there is a good chance that it will catch on.