I am not talking about what you need to save I am saying how much money you are spending, you spent £1318 pounds, if you had never purchased those phones you would have £1318 pounds in your bank account. My only point is that upgrading every year does not cost you only the price you spend that year, its a ongoing cost that adds up.
Lets use your car, you didn't buy the car for free did you? So you spend £20k to buy then you lose £10k in depreciation, so you can sell it for £10k so currently you are £10k down in your bank account still, now you buy your new car for £20k you have spent £30k of your cash.