What is the cheapest type of foam?

Cheapest type of foam is generally low density flexible polyurethane foam or expanded polystyrene EPS, also known as Styrofoam, which is inexpensive to manufacture and widely available. Open cell polyurethane foam with low density of 1 to 1.5 pounds per cubic foot is cheapest for furniture and craft use, often used in cheap cushions and packaging. EPS foam, used in disposable coffee cups, coolers, and packaging, is very cheap due to low material cost and simple manufacturing. For upholstery, cheapest foam is low density foam that compresses quickly and has shorter lifespan. For insulation, EPS is cheapest rigid foam board compared to XPS and polyiso. Polyethylene foam in low density form is also cheap. However, cheapest foam often has lower durability, lower R-value for insulation, and may off-gas more. While cheap foam saves money initially, higher density foam lasts longer and provides better support, so cheapest upfront may not be cheapest long term due to replacement needs.