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It sounds like it probably is the bearings. You know how winter tires sound on dry pavement? When bearings go bad it sounds like that, but WAY worse; like a lot louder.
If you get it done at a shop it'll probably cost between $400 and $500 but you can do it yourself for like $100 or less (Depending on the brand of bearing you get) and it's pretty easy to do. You can get away without doing anything about it for awhile though.