Apple does spend comparatively little on R&D (perhaps part of that is because they don't produce 400 different models of every darn device), but their margins on iPhones are still nowhere near 70%.
Although since you brought it up, I did a quick search and found that the margins on the iPhone as an individual product (vs. the company's overall margin) are speculated to be near 70% and that figure isn't just pulled out of thin air:
http://appleinsider.com/articles/13/09/30/iphone-5s-demand-h...