Silver is only produced when stars explode!  There's a relatively limited quantity of it here on Earth, and it is used for a wide variety of applications ranging from thermoelectric conductors to cloud seeding.  Besides these things that give it inherent value, it has been used as currency and precious jewelry for thousands of years.  Modern mining techniques and its removal from circulation in many currencies have made silver a relative bargin these days. 

I'm acutely aware of the monetary value of silver because I work with dental amalgams.  A few ounces of the silver containing amalgam "waste" can be recycled for thousands of dollars.