What are the most cost-effective options for attic insulation, including the cheapest attic insulation available on the market?

The most cost-effective options for attic insulation include fiberglass and cellulose insulation. Fiberglass insulation is typically cheaper than cellulose and is widely available on the market. However, the cheapest attic insulation available may vary depending on factors such as location and availability of materials. It is recommended to compare prices and consider the insulation's effectiveness and energy efficiency before making a decision.