I've tried selling on eBay plenty of times before, but nothing I've posted has ever actually sold aside from used video games that I was no longer playing. I think the site is good for making some extra bucks off of when you have something you no longer need or use, but actually making a business of it is pretty difficult for the average person if you aren't able to develop something yourself. Someone I follow on deviantArt has made a career out of selling her homemade stuffed & poseable animal toys. That's a case of selling your own goods though, so if you're selling something you already own you're really just making back a little bit of what you spent originally unless its a collectible that gained value.
The times I did sell games on there though, I added the shipping cost to the cost of the item itself. A lot of people are more attracted to items labelled as being free shipping, and some even mark their searches as only showing listings that have free shipping without checking anything else, so that worked best for me.