The best way I can describe what being a third party seller on Amazon is like is something like this: If you are interested in ending-up in the hospital with a massive heart attack, become a third party seller on Amazon.
This is my opinion, of course, your mileage may vary. That said, the things I've seen defy description. Things like your entire product line suspended overnight without cause, recourse or a clear and immediately actionable path to recovery. Or how about your entire account being suspended and the Seller Support people you talk to are useless?
And how about this one: How about people who never bought your product leaving negative one star reviews. Even better: People leaving reviews before they receive the product they purchased, then they cancel the order and it never goes out. I mean, think about it, as an example, say you buy a weight loss product. How can Amazon's software allow anyone, even an actual buyer, to leave a product review before they receive it? How can they allow it a week after they get it?
Here's a nice one: You manufacture your own product (not a Chinese one-in-a-thousand-copies private label product). In other words, you are the sole source and the sole retailer of the product. Nobody else makes it and nobody else is authorized to sell it. Amazon has no protections against some scammer claiming they sell your product. What happens is someone buys from one of these scammers and either get a box full of rocks, something totally different or a bad quality copy of your legitimate product. Whats worse is you are left to answer for what happened and your reputation, seller and product scores suffer due to the bad reviews.
Then there's the issue of no protection against competitors attacking your ads within Amazon. They have a pay-per-click system. You set a daily budget. Competitors will pay offshore click farms to click on the competition's ads while everyone in key markets are sleeping. By the time your potential customers wake up your ad budget is gone and you produce zero sales for your money.
I could go on. He left the platform and got really good at running his own online operation. His stress level is a thousand percent lower and, more importantly, he knows his business isn't going to be shutdown overnight by some all powerful online retail god who could absolutely ruin him. I mean, these people are supporting families. The way Amazon treats legitimate third party sellers is just terrible. And they make so much money because of them.