Double trouble but you can't clone me!

I recently watched Moon, the 2009 Science fiction film co-written and directed by Duncan Jones. If you haven’t seen it, I won’t spoil the plot, but the film follows Sam Bell, a man who experiences a personal crisis as he nears the end of a three-year solitary stint mining helium-3 on the far side of the Moon.  After a crash he discovers his double and in turn they find a secret vault containing hundreds of hibernating clones. They realize that Lunar Industries manufactures clones to avoid paying for new astronauts.  So, how realistic a prospect is this – or is it simply the stuff of science fiction?