There are third party cutting mats for the Cricut machines that work just as well as the OEM ones but at a cheaper price.
Check out Nicapa Mats on Amazon, typically on sale for multi-packs or Combo packs that include the different grips (Light, Standard, or Strong). They are 4.5 star rated with over 5000 reviews.
Xinart StandardGrip Cutting Mats come in slightly cheaper than the Nicapa mats but have less reviews. They also offer a variety of grip options to mirror the Cricut options.