Whilst I'm not necessarily happy about paying more for something, I'm not unhappy about it either, especially if Sony can maintain the recent quality of their PS Plus free game offerings. Until Dawn, Game of Thrones and Just Cause 3 are good enough to justify £50 on their own, so getting 20 other games an multiplayer as well is still good value for money.
Compare that to Xbox Live's Games for Gold programme where pretty much everything from the last six months has been indie titles and the most exciting thing in the next month is the Xbox 360 version of Bayonetta. Sure, it's a really cool game, but it's also eight years old and can be picked up cheap as chips anyway. Not really justifying the XBL subscription there, Microsoft.