Apple unveiled its US pricing plan for extended iCloud storage at today's developers launch. An extra 5GB will cost $US20/year, 15GB will be $US40/year, and 50GB (for a total of 55BG) will cost $US100 with the additional storage available for purchase via the iOS 5's settings app.
Apple users do get 5GB free and Photo Stream images will not count against your capacity. Australian pricing is likely to be different, and we'll let you know when we get those details. [9to5Mac]