Rare and other terms generally mean there is not much to compare it too. Desirability/worth can only be determined by a sale from the past or present which will determine value.There is no other way to put a monetary number on it but to try and sell it.
Be careful about the rarity values on the Hutchbook website. Those are typically the opinion of one person (the hutch specialist for that area). I know that the rarity values for the hutch sodas in the areas we dig in seem out of whack. Northern big city hutch sodas, even rare ones, typically do not have a great deal of value. Likely $10-$20 regardless of the rarity unless there are two people desperate to add it to their collection.