Final answer:
A non-essential item that costs a significant part of a person's income is best described as having an elastic demand, meaning demand is highly responsive to price changes.
Step-by-step explanation:
A product that costs a large portion of an individual’s income and is not required for survival is best described as having an elastic demand. When a product is considered a luxury rather than a necessity, the demand for it tends to be more sensitive to price changes. People will buy much less of it, or none at all, when the price goes up significantly. On the other hand, a product with inelastic demand would be one that consumers consider necessary and would continue to purchase despite price increases. In the case of unitary elastic demand, the quantity demanded changes proportionally to the price change. When we look at products that are not necessary for survival and represent a large part of the income, the demand is generally elastic because consumers can and often choose to go without them if prices rise too much.