> The cost to the original company is a lost sale, a lost product, and $20 [lost] in exchange for a 5-star review. That may well be worth it for the company, so I'm not sure this scheme would actually stop dishonest reviews, only make it worse.

Sometimes when I see a product being sold FBA I will do a search on Alibaba (they’re always on Alibaba) to find the wholesale price. I’ve found that the markup on most products is high enough that if a seller were to give every buyer $20, they’d still be making money.