I forget what we used to charge because it's been 3 years since I did that stuff...I actually think we did 25% or 50% on the price. Then again, we were selling items that we had to take pictures of, make descriptions for, and do the whole selling process with, and not everyone has thousands of feedback on eBay. For domains 10% is pretty good, though I would only suggest going through someone to sell a domain on eBay if it's a really high quality one (4-figures or more) because eBay is generally not the best place to sell a name worth less than that. Keep in mind that with the eBay fees, that comes out to more than you would pay selling at a place like Afternic or Sedo.