I think £252 makes a better headline.
I thought that el Reg would have dug much deeper than this. It's really quite simple: the iPhone tariffs are each priced at £20 over the corresponding simplicity/SIM-free tariff. Since the iPhone is "unsubsidised", it stands to reason that premium is used 1) as payment to Apple, 2) to offset unlimited data charges, and/or 3) extra margin to O2. The rumoured "up to 40% to Apple" figure converts to £14/month, which fits rather tidily within the £20 premium, with an appropriate payment to The Cloud to spare.
1500 words on that here: