Got a source for that? The iSuppli teardown doesn't indicate that.
the iPhone 5 costs $180 to manufacture and sent through the supply chain. the base model, where the least profit margin is made, is sold for $649.
469 / 649 = 72.265% --> the least profitable 16GB model
the profit margin soars when people pay an extra $100 for the 32GB model and an extra $200 for the 64GB model.
source: have you ever used google?