What costs do I as the seller incur?

There's the rub. eBay charges, or more to the point rapes their Buyers 10% of the final cost and Pay Pal does the same with 3% of cost. FYI, eBay owns Pay Pal. So they are essentially raping you twice. That's why I suggest you ask for more on your item to offset those charges. The only reason why I use eBay is because they have the most subscribers with translate into more views which of course increases my chance of selling an item. You can always use Craigslist for free, but you run the risk of having to ask for far less as well as less people seeing your item.