.......The esp chip and boards inside these are just pennies.
Exactly! Every maker of any and everything electronics relayed is producing these device (I would imagine through a 3rd party vendor). And EVERY business of any type/size has servers. So the apps/skills/etc. is all a nothing burger for cost and expertise. Like USB and phone accessorizes found in Dollar Stores.... these devices are everywhere.
What makes Home Automation "
Automated" is the software.... or in the modern world...
the server software. And what your still calling voice assistance.... has long been a product integrator.
These items aren't selling by the pallet, or even the truck, ship, or warehouse full. This is now a multi-BILLION dollar industry.