Barring actual manufacturing defects, the cheapest quartz crystal timing circuit on the market will be far more accurate than the very best Swiss watch movement, by orders of magnitude. A mechanical watch depends on a spring whose behavior is highly environmentally dependent - it will gain or lose multiple seconds per day, being affected by the orientation, vibration and temperature changes it experiences. A quartz watch will drift a few seconds per month.
I think mine was a couple hundred bucks. People mistake it for something fancy, but it's still cheap enough that I don't have to worry about damaging it. Also you can get spare parts for Casios!