People often over-value things the first time they sell things on Ebay. You have to check to check what similar items have gone for in the past. That will give you a good indication of what you could get for yours.
Things are only ever worth what people are prepared to pay for them. But I think we've all been in the position where we've sent something out for free, or for very little profit by the time fees are taken out. And sometimes it's the most divine stuff. I always count those as my karma sales. At some point, I will have a purchase or two that matches them.
As someone else said earlier, you have to word your title carefully to attract attention, present your items attractively to ensure maximum confidence in the buyer and you need to put the right seasons clothes in at the right time, just before the appropriate season starts or just at the beginning of the season.
With Ebay now I try to sell just what I'm happy to give away. That way, if it sells for anything, it's a bonus.
If what I'm selling has a definite value to it, I'd do it on a buy it now price or set a high start price.
Generally, with clothes, I start at 99p and accept that that's what they might go for. 5 years ago kids clothes got bonkers money. Now, every supermarket in town sells nice quality clothes in great designs that are near enough at disposable prices. How do you sell second hand stuff against that????