The problem with EBay is actually having things sell. I've run into that problem from time to time, where things simply sit there. Even if you have them listed at the lowest prices, they just go without bids or sales and you have to go and re-list them again. I actually don't do bids anymore. I only do Buy it Now since they started letting you list Buy It Now auctions for free.
Still, after awhile, you end up with all of these Magic cards you could never sell unless you listed them for $1 or $2 with free shipping. Unless you're selling ridiculous volumes of these cards, the shipping and packaging costs alone - even for a simple white envelope, top loader, and stamp - end up far outweighing the actual profits. You actually put out more money than you make, which unless you sell 100's of cards daily, it's simply not worth it.
I've never bothered becoming an eBay Power Seller because I simply can't be bothered with making .25-.50 a listing. Take into account also that PayPal takes about 40 cents off of any payment you receive as a seller, not including the EBay 10% final value fee. So, I get stuck with hundreds of Magic the Gathering rares that I simply take to a local game store and sell them as bulk.
I'll only get about 8 cents a piece cash for most of them if I sell them to a vendor. But, why go and buy all those envelopes, stamps, and top-loaders? Usually, selling Magic cards to vendors isn’t worth it to me unless I have enough bulk cards to get some pocket money in return.
Overall, though, it's much, much better to sell cards on EBay than it is to sell them to vendors. The payoff from selling cards on EBay (as long as you can sell them for about $3-4 or more) is far greater than dumping those cards for a quarter or so a piece. For all of EBay's faults - and it has many - it's still the best place to get rid of extra cards you don't need anymore.
Have any of you ever made successful sales on EBay? Do you know anyone that practically makes a living off of it? I'd love to know. I'd love to make a living off of selling cards on EBay, but it just seems like such a hassle!
Photo credit: Wikimedia Commons