Well, there wasn't much warning on this one was there. Sony has announced that the price for PlayStation Plus will go to $59.99, up from $49.99, for a yearly subscription in the US on September 22nd. If you want to pick up a 3 month pass, that'll cost you $24.99, which was originally $17.99. Those that just want to pay on a month to month basis will see the same price of $9.99.
Usually, we see a lot more advanced warning when we get price increases. A month is rather short to spring this on folks and I'm sure there are plenty of people now picking up PlayStation Plus cards at its current price.
The price increase brings it in line with Microsoft's 12 month Xbox One Gold membership.
You can usually find deals on these types of things, but deals after the price increase will probably bring it back down to its original pricing. Of course, you have no choice but to pay Sony if you want to continue to get and access their free monthly games and play online.