If it's GPL, or AGPL, someone can sell a copy on Amazon, but it's pretty pointless because the person who buys it is allowed to give away more copies for free.
If it's MIT, the person who buys it ISN'T allowed to give away more copies for free if the seller doesn't want them to. MIT means SOMEONE ELSE can (for all practical purposes) copyright YOUR software, and all you get is your name in a notices.txt file.
> If it's GPL, or AGPL, someone can [...]. If it's MIT, the person who buys it ISN'T allowed to [...]
MIT gives strictly more rights to the user than GPL. If you can do something under the (A)GPL, you can definitely do so under MIT. In all cases, as someone who receives a copy, you are allowed to sell copies regardless. Under the (A)GPL, you will need to provide the sources on request as well.
> MIT means SOMEONE ELSE can (for all practical purposes) copyright YOUR software
You always keep the copyright on your code (unless there is a copyright assignment), regardless of the license.
MIT allows someone else to not share the source when redistributing some software under MIT or a derivative.
MIT gives the user the right to take away another user's rights, potentially leading to fewer rights overall.
I give foobar to Alice under AGPL. Alice gives foobar to Bob, Carol, and Dave, under AGPL so I don't sue her.
I give barbaz to Alice. It's MIT. Alice gives barbaz to Bob, Carol and Dave under a proprietary license. I can't do anything about it, because I gave her that right.
If it's MIT, the person who buys it ISN'T allowed to give away more copies for free if the seller doesn't want them to. MIT means SOMEONE ELSE can (for all practical purposes) copyright YOUR software, and all you get is your name in a notices.txt file.