If you used large enough resistors in the divider you suggested this wouldn't waste much power. Using too large of resistors however will make the circuit more susceptible to noise and humidityr.
One other idea that comes to mind is to use a TVS diode rated at 230V in series with a resistor divider. To my understanding these are a lot like zener diodes, but come in higher breakdown voltages. Therefore, there would be no current flowing through the divider while the input voltage is under 230V. Unfortunately for values above 230V this circuit would have the same draw backs mentioned before. I'm also not sure how precise TVS diodes values are rated for.