$1000 says he isn't.

At 3 cents/word, not only is the ghostwriter not an expert, they probably aren't even a good writer. That's less than what a decent typist would charge for material that's already written (transcribing from audio or handwritten manuscript).

Maybe. Looks like the OP says his books are pretty good with high ratings and a high volume of ratings as well, so they must be enjoyable enough to the people who buy them.

I’m sure we can trust the self publisher of a ghostwritten unedited cost-first keyword-selected book to never employ fake reviews. He’s only here to provide what’s best for his customer.

That's pretty disingenuous to say they employ fake reviews, regardless of whatever your opinions of self publishing are.

Why is it disingenuous? They've literally described a process optimised to produce "passive income" with absolutely no quality control at all.

Selection bias. People who see OP's books in the search results and conclude it's a shitty book/something is off/etc are not going to leave a review (on a book they didn't buy) to say so. People who spend $10 and 4hrs of their time are inclined to not want to feel like they just wasted that and so will positively review something to reinforce.

Since the person promoting the book has literally no interest in the content, it doesn't make sense that the writer would be an expert, nor that the book would be any good.

An expert ghostwriter would be undercut by a ghostwriter supplying copy-pasted material just good enough to get past the publisher. A publisher who actually cares about whether or not the book is worthless would outbid this publisher for the skills of the expert.

You hire ghostwriters through freelance sites so it’s possible but for sure not a given the ghostwriter will be an expert. It’s more likely the author would do a lot of web searches and cobble something together that’s most likely or some value but it’ll likely be a got-what-you paid for situation.