Oakleys are indeed good quality, but getting them glazed up via the internet kind of defeats the purpose, sure there is lenses in them but do they take the curve of the frame into account ? Are they centred up correctly, chances are not thus the wearer can experience induced prism resulting in eye fatigue!
Sure, there is a profit margin in optics but there is one in any business. High street rent has to be paid for, test room equipment costs an absolute fortune etc etc!
Also, the more expensive your glasses the smaller the profit margin will be, so you could argue the more expensive the better value for money your getting!