I have twice sold items on eBay. Items that I used and no longer needed. On one occasion I sold my desktop PC after I bought a laptop, and on another occasion I sold my Nokia 1100 phone after I upgraded to a Sony Ericsson k750i.
On both occasions, eBay charged a hefty sum as charges for selling my items through eBay. I sold my desktop for Rs. 9000 and was charged around Rs. 350 for that. I sold my mobile phone for Rs. 1500 and was charged Rs. 90-odd for it.
When I first sold an item on eBay, I did not know that I would be charged for it so heavily. I dont know what is the fee structure, because though I opted for some highlighting for my advertisements, that was nowhere as expensive as to warrant a bill of Rs. 350. I wonder what is the percentage of selling price they charge as fees.
Anyway, this was sometime in 2006. Now of course, I would not use eBay either as a buyer or as a seller. As a seller, I would prefer to advertise my items on a free and popular service like Craigslist.com or Sulekha.com, both of which have city specific classifieds. Most of my colleagues too do the same. Only disadvantage is that only people in your city would buy it, but thats fine anyway as normally any casual seller would not want to take the responsibility of shipping the item to the buyer.
Even as a buyer, I would prefer to buy an item from a shop in my city, so I can inspect the product carefully while purchasing and also take it there if I face any issues later. So there is some safety built in to this method. I would buy something online if and only if I couldnt find it in my city. And even then, I would buy it from a seller based in my city. This is much better than buying from some seller based in some other city, and then sitting and crying later if something goes wrong! And as is evident from reviews here, that seems to be a common phenomenon.
But just a tip for those who still think eBay or other such sites offer good deals on some items. Better to discuss with your colleagues or on a discussion forum and get some IDs of reliable sellers and buy only from them, rather than buy from some unknown seller even if they have a 99% or 100% positive rating.