Different products have varying price elasticity of demand (PED) based on availability of substitutes, necessity, and consumer behavior. Beef and steak have elastic demand because they have many substitutes, and steak is a luxury item, making consumers sensitive to price changes. Public transportation and gasoline are inelastic since they are necessities with few substitutes, meaning price changes do not significantly impact demand. Pencils have unitary demand as they are low-cost, frequently purchased in stable quantities. Housing can be unitary or inelastic, as it is essential, but high prices may delay purchases rather than reduce demand significantly.