There is almost no way anyone outside of high level Apple executives that would be privy to their estimates for margins on individual iPhones including R&D and other costs. Especially because a lot of Apple products' value proposition comes from the ecosystem of their services, including the ability to visit a retail store and talk to a W-2 employee of Apple (which sets them quite apart from basically every other electronics brand).

You can see their overall profit margin though, which they keep around 25%:

https://www.macrotrends.net/stocks/charts/AAPL/apple/profit-...