The store format is where a seller pays fixed rate a lower per item listing fee.

The concept is that you can list items in a custom store. You can use categories for your store. These are much like departments. With in the categories you can list items at fixed prices. The listing fees are lower than in the auction format.

Opening an eBay store:

The costs are $15.95 , 49.95 and 499.95 a month depending on the store type. The first 30 days are free of charge. eBay Stores subscribers can list in the Store Inventory listing format in addition to the Auction-style and Fixed-Price listings. The Insertion fees starting at $0.05 for any single item for 30 days, Store Inventory is the most economical way to list good for sale on eBay. You set the price and it is listed for 30 days. You may list good in any quantity and they can see set to renew every 30 days if you wish ( standard eBay fees will apply)

What are the listing  (also referred to as insertion) fees?

Insertion Fees
Starting or Reserve Price 30 days Good 'Til Cancelled*
US$0.01 - US$24.99 US$0.05 US$0.05 / 30 days
US$25.00 - and above US$0.10 US$0.10 / 30 days

In addition to the listing fees there are also selling fees if your item is sold. The are called final value fees. These are rather difficult to figure out.

Closing Price Final Value Fee
Item not sold No Fee
US$0.01 - US$25.00 10.00%  of the closing price
US$25.01 - US$100.00 10.00%  of the initial US$25.00 (US$2.50), plus 7.00%  of the remaining closing value balance
US$100.01 - US$1,000.00 10.00%  of the initial US$25.00 (US$2.50), plus 7.00%  of the initial US$25.01 – US$100.00 (US$5.25), plus 5.00%  of the remaining closing value balance US$100.01 – US$1,000.00
Over US$1,000.01 10.00%  of the initial US$25.00 (US$2.50), plus 7.00% of the initial US$25.01 – US$100.00 (US$5.25), plus 5.00%  of the initial US$100.01 – US$1,000.00 (US$45.00), plus 3.00% of the remaining closing value balance (US$1,000.01-closing value)

Why would you use an EBay store over EBay auctions? If you what you want you can reduce the costs of listing. This works great if and item does not sell but there are negatives too. The traffic in the stores is not a good as in the auctions and in addition the final value fees are higher. Still if you have a item you will be selling over and over again then you will want to consider the ease of use the eBay store format.

I have opened an eBay store an find it to be the most economical way to sell goods but the downside it sometimes things take longer to sell.

The bottom line: I would recommend an eBay store for anyone planning to sell more than 50 items at any 1 time.