There is no charge for listing on Amazon.
However, making a good amount of money will be dependent on your description and trust worthiness. There are ALOT(!!!) of bootleg and lazy sellers on Amazon (relative to Amazon).
For example, my mom wanted this DVD, she sees that it is only a few dollars on Amazon marketplace, so being the
CheapAssMom she is, buys it. It comes and is obviously a bootleg. It would not even play in our DVD player and the cover art was a joke. She requested to return it and it was easy as pie. She got her money back and bought it at Hastings with the buy-2-get-1-for-a-penney deal they always have on clearance rentals (previous rentals).
Another example, you can get really cheap books off Amazon for school. When you see a book selling for over a hundred brand new or even over half that brand new and the lowest prices on the marketplace are $5 and $10 it is almost a given that it is the international or a previous edition. But the sellers don't say that in their description. They just hope you don't request a return. The international edition is exactly(!) the same as the hard cover, but uses cheaper paper and is paper back. Some people don't know this or don't care.
So, from my experience to be successful on Amazon you have to set a fair price for what it looks like legitimate sellers are selling for. If you are near the low end (which is usually way higher then ebay or Half) you sell very quickly.
Anyway, I have had nothing except a good relaxing and stress free relationship using the Amazon Marketplace. Listing is easy. No fees and I can relist a hundred times if I so please. I can change the price and description at any time.
The only downside is they do seem to get a pretty big chunk (~15% - 20 % it seems) of the final sale (shipping included).
The shipping they provide is for the most part adequate. The shipping Amazon gives you varies, depending on the item. Media items (books, DVD, ...) seem to get $3.49 for normal shipping and $5.49 for expidited. For these I just use media mail and pray that the book fits in the flat rate priority mail envelope respectively. Non-media items get more for shipping (my computer hardware I sold was < 13 oz so I did 1st class at $2.xx but was given $4.99 from amazon for normal shipping).
I am not saying Amazon Marketplace is great, but I like it better then ebay for a few reasons. Those reasons are why I don't sell nearly as much as I would or could. You might make more on ebay due to the Amazon fees being so much, but if you list it as an auction, who knows how much you'll sell it for. Which is why I have not listed anything on the bay for a while now.