I've no idea of the cost but have often wondered why it is not a common practice in this country. Nearly every house I saw in Western Australia was fitted out with a reticulation system, at least that is what I think they called it. I assume the rest of Australia had the same systems in place. Gardens were watered by sprinkler every evening after the sun had gone down, for an hour or so.
I would be interested if it is reasonably priced in this country.