And I'm not talking about really cheap quality materials either. The ones I'm ranting about, have a fair amount of time consuming details, are using gemstones/and or Swarovski crystals, hand embellished brass, handmade sterling findings - stuff that 1) either costs a fair amount, and/or 2) takes a fairly long time to make.
These sellers for one, are not calculating the time it takes to make a piece of jewellery, and 2, are forgetting about the time it takes to post something for sale on etsy, or artfire, or wherever it is you're selling.
If it's a one of a kind piece, keep in mind that it can take well over an hour to take pictures, edit said pictures, write a description, and post it on etsy. If you are making multiples of an item, that cost goes down considerably. There is also the time to make the item. A lot of these items that I'm seeing are not even doubling their costs over volume wholesale prices for the components. Then take off the etsy, and paypal fee's. They can't possibly be making a profit - at all!
Some of the sellers that I most admire, are selling their jewelry for much higher prices, and they're selling. Many of these people have thousands of sales under their belts. If you value your work, others will as well.
A few things you should look at before you start selling:
Make sure you can make a profit - you need to be able to take some home, you need to be able to restock, and you need to be able to pay your fee's at the end of the month. I'll bet many of these sellers are only taking care of the last two items.