Reviews on Amazon are heavily gamed and you should not trust them at all. I get little business cards offering gift cards for 5 star reviews regularly. Product listings get swapped for entirely different products while the review stay.
What works for me is, the reviews should fall off like a neat stair case, 5s the most, then 4s, 3s, 2s and 1s. If the 1s are bigger than the 2s by a lot, it's usually the classic "Sell 500 good quality ones, get the reviews, switch to the knock offs".
