On the average, based on estimates from those in the professional photography industry, 1 image out of 100 is going to turn out absolutely perfect.  If you fire off 200 shots during a shoot you’ll have a few that are outstanding.  But more on that is that you’ll probably have 3-5 others that really stand out, while not matching the first few you chose.  Is it realistic that you only have 10 awesome images from a shoot?  The answer is “Yes”.