2004 Toyota Sienna Axle Bearings and Ruined Tires

Drive Train Axles Bearings problem
2004 Toyota Sienna Four Wheel Drive Automatic 95000 miles

I took my car to a Le Swab to get it aligned, having been told that there's some misalignment b/c my rear tires have unusual wearing. So when they tried to align it, they reported that I have a problem with my rear bearing, that it was loose, and that it needed replacement, and it will cost $550. They said the test show some problem. That when I turn my car to the left at about 30-40 mpg, there's a growling sound. The mechanic drove me around and asked me to listen to the sound, but I really couldn't hear anything.
I wonder if perhaps i'm just a bit deaf, or am I being scammed?
Would appreciate some feedback on this. Thank you.