Answer:  As a starting point a well-made custom guitar will cost ~ three times the materials cost.  An instrument from a well-known luthier can cost four or even five times the materials cost.  If the other materials cost $700 and the guitar has $1,500 Brazilian Rosewood back and sides you can see why a custom Brazilian Rosewood guitar can cost seven to ten thousand dollars. So the answer depends on what kind of guitar you want.