Real slate comes from natural stone. Synthetic slate comes from various sources made to look like slate. For either hard or soft natural stone, expect to pay $10 to $30 per square foot, each of which will last 50 to 200 years. If you choose synthetic slate, budget $3 to $16 per square foot for recycled asphalt, metal, or fiber cement. These options will last 20 to 50 years.