Amazon calculates a product’s star ratings using a machine learned model instead of a raw data average. The machine learned model takes into account factors including: the age of a review, helpfulness votes by customers and whether the reviews are from verified purchases.
Build quality is decent for the price, but don't go in expecting a top of the range boxed clone. My controller arrived in bubble wrap only, this is not a boxed product which is something to be aware of. Other than that, it works as expected, and you can't beat the price, although I'm not sure why different colours cost different prices.
I've only had this controller for a few hours but I already really like it. Build quality is fine, neither outstanding nor poor, and it functions exactly as it should when emulating N64 titles with Project64 v1.6 on Windows. Absolutely no complaints for the price.