Because the chance of a fire is small, your premiums will not be that much and should not detract much from your overall business profitability. Part of the insurance premium paid is compensation for the risk the insurance company is taking to insure your manufacturing plant. A smaller part is a reasonable profit for the insurance company underwriting the policy. You should consult a trusted and knowledgeable small-business insurance agent to discuss your company's insurance needs. Your banker is one good source of possible insurance agents.
Some possibilities are very expensive to insure against.
You might find that you can't afford some particular insurance which you feel your company really needs. Some business owners try to set aside money to cover such a contingency. If the cost of the insurance is too high for your business, it is unlikely you will be able to set aside enough money to cover an occurrence of that contingency, either. For example, imagine saving and setting aside enough money to cover the rebuilding of your manufacturing plant. Recall, this is something easily and cost-effectively insured.