Condoms are most expensive when purchased at a retailer in a small quantity. At Walgreens, the price for a box of three lubricated Durex condoms is $3.99, or $1.33 per condom. The price for a box of 12 of the same type of condoms is $11.99, or about $0.99. A box of 24 Durex condoms, on the other hand, is $15.99, or $0.67 per condom. The difference between the price per unit on the box of three vs. the box of one dozen equals $0.34, for a 25.5% discount. When purchased in a package of two dozen, the price drops $0.67 from its high point  more than 50%.
Key Difference: The Lower, Middle, and Upper Classes are basically groups divided by income. The lower class usually earns the least, the upper class earns the most, and the middle class earns in the middle of the two. The population is often divided into socio-economic groups based on their household incomes.
Definition of middle-class : of or relating to the middle class; especially: characterized by a high material standard of living, sexual morality, and respect for property middle-classness