I wonder if this includes inactive sellers.
In 2014/2015, I would buy insurance cargo from truck accidents: I had the space and the ability to grab and store the items until I could resell them via secondary means: This usually meant working with buyers at stores like BigLots and other discount stores, but, occasionally I'd get electronics (which isn't something that those stores really wanted).
I came across a huge lot of LG monitors that were involved in some fender-bender. Out of the lot of approximately 24 per pallet, only two were visibly damaged, and I had 12 pallets worth of monitors and the cost per-pound evened out to approximately $35/monitor.
I would sell these monitors, which were retailing for right around $200/each new, for approximately $150 in "Open Box" condition on Amazon, and would consistently sell anywhere between 8-10 of them a week.
Amazon charged me:
Cost for getting my items to Amazon (Usually around 9-11/each, depending on season and how busy UPS is), Cost for storing my item in their warehouse (usually around $2-4/month, depending on season), cost for picking and shipping my item (around $30 because it was considered oversize), and the constant reminder that these weren't my customers, they were amazon's customers (customers would "return" items, so, I'd get the entire cost of the item removed from my seller account, because, Amazon wouldn't eat their own fees here, and then have to fight them to get my money back when that customer wouldn't return the item). Amazon also fiercely competed with me on these monitors -- they'd knock down the cost of their "new" items down to what my refurbished cost would be...cutting me out of the 'buy box,' but, losing what I can only assume is about $30+ per monitor wasn't something that they did for long, as after a week or so, the price would be set back at MAP until I'd go and build a new shipment of items into Amazon, set a price lower than theirs, and then they'd automatically bring down their pricing to meet mine.
Amazon's profit to me would be around 40% -- around 80 dollars.
In 2016, Amazon changed the rules so I couldn't sell the items as "Open Box" and would have to sell them as "Used" because I didn't qualify under the rules as a refurbisher.
(admittedly, by that time, I transitioned away from selling items on Amazon and use a different channel for the sales of these items).
There are a lot of snake oil salesman selling "how to make money on FBA" videos and courses online, but, the reality is that the only entity who makes money selling new items on Amazon is Amazon.