Mainly for those who still like to buy a monthly gaming mag I guess, though if you do then it's a pretty good deal. You get 6 issues of Official Playstation Mag, with Metal Gear Solid V for PS4, and also the Limited Edition Steel Box.
The magazine itself retails at £5.99 per issue, and average price for the standard edition of MGSV anywhere (brand new) is around £18-£20, so you're getting around £54 of stuff for £29.50, plus the Steel Box. Oh, there's also some free PS4 thumbgrips coming with the next issue (due on 30 August I believe).
Also if anyone's curious, they despatch MGSV seperately - I got mine with the steelbox within a week of placing the subscription, so you don't need to wait until the first issue comes to get it.