Let's use your example. The sellers should stop selling that item on Amazon, and sell their light bulb on Walmart, or where-ever. Customers who really need that will go find it at Walmart, or where-ever. This strengthens the competitors to Amazon, which is bad for Amazon and good for the consumer. The consumer also find the lower price that they wanted. Alternatively, they buy the alternate product on Amazon which would be cheaper than the inflated price (per your example). Again, good for the customer. Everyone wins in every scenario except for the seller, which is how Amazon and every wholesaler operates.
Suppose the FTC wins this case and sellers can put whatever price on whatever site. Amazon, like any store wants the lowest price. Not to mention there are only some many items you can show on the first page of results. They will find some other reason to remove these sellers and/or their items.
Now maybe there's another case to stop that behavior too. The result is that companies are not obligated to let sellers on their site. That is insane.
In summary, there will never be a scenario where Amazon allows sellers to sell the exact same item for more than Amazon's competitors, unless the government forces Amazon to let sellers sell whatever on their site.