What are 'cheap' Shahed drones, used by Iran in Middle East war?

Iran has used its Shahed drones to attack countries in the Middle East including Bahrain. The Shahed series are cheap, mass-produced and expendable weapons that act as a combination of drones and cruise missiles. Shahed-136, which can reach a maximum of 2,500 km, and Shahed-131 are designed to carry explosives and hit fixed targets such as buildings or military sites.