Rise of living cost

My aunt came back from US for a two weeks vacation, she was telling me that the cheapest gasoline in Oakland cost USD4.00/gallon now, compare to around 1.89/gallon about five years ago. She said that things like rice, eggs, milk all had gone up for more than 20% since I left. Part of the reason is also because of the weakening USD, but somehow I do think that the US government purposely did that. Two simple reasons are: 1. Crude oil was sell in USD. 2. Trade activities with China need to be balanced, if RMB doesn't appreciate at the pace as the US government want, they shrink their own currency value.... Well... it is just a simple thoughts of mine, I am not good in economics. :)