Mattresses

Cost to make a mattress: Anywhere from $75 to $150

Price you pay: $200 to $4,000, depending on the brand

Materials for manufacturing mattresses are cheap, and the cost to make a mattress is usually around $100 no matter the price you pay. There are also just a few companies (e.g. Serta, Simmons, and Tempur-Pedic) that have a monopoly on the industry, making it hard to comparison-shop.