From the day of release, you get about seven years before you stop being able to upgrade to the latest iOS version. Say you pay £800 for the phone and keep it for the full seven years, that works out at about 32p a day. For something that is increasingly integral to modern day life, that's a pretty good deal. That's also not accounting for the fact that you could sell it on for between £50 - £100 or keep it as a fully functioning device for a few more years, both of which make it even more economical. Add on the fact that you generally get tighter security and higher quality applications because there's more money floating about in the ecosystem which attracts more devs then, if you can afford it, it's a no brainer in my opinion.
