This feels like one of those threads where people are arguing even though they don't really disagree on anything. Let's establish some facts here:
1.) Tom Brady is selling a book/lifestyle
2.) That book contains some things that are true, and are consistent with medical science in terms of health and diet
3.) That book also contains some things that are false, or at best dubious claims that are not supported by research
4.) That book also contains some things that sound silly and may be unproven, but could legitimately work for him
5.) Tom Brady's continued excellence at a relatively advanced age may be a reason for him, and others, to believe that some or all of these things are having the desired effect, but it is proof of exactly none of them
6.) There is nothing wrong with the price point, $20 is right around the average for a book
Now, do I think that drinking water prevents sunburns? No, I don't. But, do I think that if you actually lived the total lifestyle that book recommends you would be way healthier? Absolutely yes. While it may be sprinkled with some goofy claims that are fun to point out as snake-oil, 95% of it is not controversial. I'm not gonna buy it, but that's just because I don't need to pay $20 for someone to tell me that to be healthy, I should quit drinking and work out for four hours a day and stretch more and eat well.
What's the argument here? That Brady should be ashamed to be selling a book that contains falsehoods? I guess so, but that applies to basically any book that is about helping people, from diet books to management books. Also, I'm not sure that there is a harm here. If (gullible) people buy the book and do what it says, it sure seems likely that the positives will outweigh the negatives.