Tom,
Unfortunately, such are the demands on the superintendent to make that decision when the pro shop/GM is struggling to meet their rounds quota/budget goals.
Gets to be pretty siginificant....assuming a booked tee sheet, approx every 10 minutes of frost delay the course is losing $300-$400.
On the positive side, once the greens are more or less unfrozen/unfrosted, I have yet to see any damage from playing on frost in other turf areas created by NON-CART traffic that I would classify as significant enough to put a real hurt on the conditions of the course.
Now.....I do have some pictures of what happens when you send mowers out too early or when cart-riding golfers fail to abide by the "Carts on paths only" rule.....yet another point in favor of focusing on letting golfers walk instead of ride.