Some markets require proof of insurance-- usually they mean general liability ("slip and fall" insurance) in case someone injures themselves at your booth. This can be added on to your homeowner's insurance as a rider for virtually nothing.

Product liability ("eat it and die" insurance) is an entirely different type of insurance, averaging between $400 & $1000/yr US. Larger shows usually require proof of this. (and if you wholesale, you definitely want to have it as a standard "good business" practice). It would cover injury to a person due to having used your product. How much you need it is really up to how much risk you're willing to assume with your product-- personally, I would want to assume zero because I don't know (1) if a person will be sensitive or allergic to an ingredient I've used, (2) how bad that reaction might be (minor discomfort or life-threatening) or (3) how litiginous said person might be.

That said, how much of a "business" is this market going to be? Will you make up the cost of the insurance? (you do have to renew it every year.) There is no question that small business have a huge struggle with these "administrative" costs and sometimes we end up taking the risks & hope nothing happens until we can afford to do everything "right".

Unfortunately, this is all your call. Good luck.