It depends on what you mean by expensive. It would probably be cheaper to go wireless like this than to hire an electrician to run romex.
But I just keep running wires. Gives me a good workout, so I don’t need a gym membership or an expensive mountaineering bike to keep fit, Increases the value of the house when done well, cuts down on my carbon footprint and energy bills, leaves more wireless bandwidth for other purposes, gives me another set of fallback career skills, there are lots and lots of reasons not to count the hours I put in. And once you aren’t counting the hours, buying wiring turns out to be incredibly cheaper than buying batteries over the lifetime of the wire.
If you rent, none of the above applies - unless you can get the landlord to pay you for the work, which I used to do when I was a renter.
