Probably part of it. A lot of reviewers get their units for free and it's easier to be happy with something you didn't pay for. We can't tell which reviews were sponsored, so we can't measure that directly.

One unfortunate thing is that Amazon blocked all reviews that said "In exchange for an honest and unbiased review, I received ..." which was a good marker of product crapitude. It makes sense for Amazon to do that since it makes them look better but as a user I wish it hadn't happened - because of AI I can now review all the crap reviews easily. It would have been good to have known.

“Sponsored” is an interesting word to use