There really is no rhyme or reason to Ebay. I have been selling DD's outgrown clothes on there for 7 years now.
Sometimes, I make crazy money....like when someone bought a
DisneyStore Cinderella dress and cape for $120....yep, I paid about $50 for the two of them brand new.
But then, a Ralph Lauren 3T dress wouldn't sell. But my son's Gymboree button down sold for $12, more than what I paid new.
I have listed in lots, but also single items. Be careful on shipping....I won't personally bid on anything with what I feel is ridiculous shipping....like $5 shipping for a leotard. That's going to cost $2 in a First Class envelope, and if you count the envelope and label, $2.50.
Weigh the items before you list them and go to usps.gov and figure out shipping to somewhere across the US from you, not in a big city, but a smaller metro area like Kansas City or Ann Arbor, and type in the weight. I have a small postal scale so it's easy for me. Anything over 1 lb is Priority Mail and starts at about $7.50. If I do a lot, I'll break it into 2 packages under 1lb each and charge $6 to keep costs down for buyers. I only charge for shipping, what it costs me.
Listing is generally free, but if you sell it, you owe Ebay 10% and paypal another % (don't know how much). I figured out that I had to sell items for $4.99 to make it worth it to me....that's about $4 coming back to me. That does not include shipping. So I don't list things at .99, because they may sell at .99 and then I get like .75 on it.
I don't sell Target, JCP, Kohl's on Ebay. Nobody wants it. I sell Ralph Lauren, Gap, Hanna Andersson, Hartstrings, Gymboree, Disney, Tommy H, and brands like that.
I do Ebay because the one time I went to the consignment store, they were nasty, and offered me $2 for a Ralph Lauren NWT shirt. Sold it on Ebay for $16.