That's rather how a lot of Amazon reviewers are. Vine-rs are also now the only group of reviewers that can officially review products for free. Naturally when you are getting something for free, it's hard to really take value into account. A lot of 2-star $100 products might be "5-star" if you pay $0. That's something Amazon recognizes in its own policies towards normie non-Vine reviewers.

Absolutely, but it makes Vine-reviews useless to me. I'd take the product for $0 and be happy, but they aren't offering it to me for $0, so some review that's essentially "it was free, it's fantastic for something that was free" isn't relevant.

Maybe it's just not an issue for most people because they don't know that reviews could be bought, so any and all reviews are great for making the sale from Amazon's perspective. If the minority that chooses to shop elsewhere grows too large, they can always make a dramatic gesture, punish a dozen people with fake reviews and donate to a children's hospital.