And that's why non-economists call economics a "dismal science". What Barkley gets for endorsing whatever is not the same as $30 an hour for sweeping the floors. To him, and to the thinking people who won't buy such products because of endorsements (there are a few of them), it is a scam.
I respectfully disagree. Let’s say you own an acre of land and I am familiar with every stick and stone on that property. I also know what every nearby property has sold for. Property normally sells for a thousand an acre. For whatever reason, I really want that property you own. You offer to sell it to me for a million dollars. I buy it from you.(This is theoretical—I’m not a rich man.) You would have taken much less, but will gladly take a million.
Have you scammed me? I would argue no. Many would call my preferences foolish, but I had free choice and knew what I was getting.
In the same way, we might saying that someone is foolish for buying a weight loss product because Charles Barkley loses weight. But the facts are in front of them. They are willing to pay a little bit more because of Barkley’s endorsement. We can’t question people’s right to their preferences on such matters without questioning the whole idea of freedom itself.
Many people feel this way, and therefore, Barkley’s endorsement is worth a great deal. He is able to meet the preferences of many people for doing very little work. We may not like that the income appeared to exceed the effort, but it was a legal exchange of goods with full knowledge on the part of all involved.