Here is a question to ask yourself: are you at a time in your life that if there was a catastrophe and you lost everything would you replace all that you lost, or would you move onto a different phase of your life? Dependent on your answer is how you can apportion a monetary value as to what you need and therefore cover. Yes, as you add value so the cost to cover goes up also in your case the machinery is not what would be considered "normal" for a garage so the inherent risk associated with it goes up too.
