[j-c-hewitt]

One way in which Amazon has restricted this type of gaming is by restricting the ability of sellers to apply extreme discounting. Even legitimate attempts to do this such as liquidation can result in a warning from Amazon about rank/review manipulation.

However, real crooks just compensate verified buyers by paying them via Paypal, Payoneer, etc. You can't protect against that except through court order or by private sting investigation. Amazon does sue organizers of these schemes and has untangled some in that way, but that is challenging to scale.