I'd like to disagree with an earlier poster. I don't want to make a 'small' profit. I want to make a BIG HONKIN profit. 
I notice that seller is able to make multiple sales to the same customer (not usually possible with my lines) so his total may make a small profit on many items worthwhile. Certainly scrapbookers find that is true, for one category.
But don't mistake 'profit' for 'markup'. You have to work out all your costs before you can set your asking price. And I would argue that that includes your time. Here in Ontario Canada our minimum wage is 17 cents a minute. ($11 an hour). So if it takes you half an hour to photograph or scan your item, write the description, add HTML coding and fill the Sell Your Item Form, then 15 minutes to package, weigh and measure the parcel, Your item has cost you $7.65 before any other costs like eBay fees, procurement costs, and postage.
You will get faster at listing as you get used to it. Like anything else.
Another point, the more items you have for sale the more hits you will get. The minimum number of items in a Store to be economical is supposed to be 54 unique items.
Put a link to your Store in every listing (one of the few links we are allowed).
I really saw a drop off in sales when I removed all my book listings prepratory to moving across the country this fall. I went from nearly 3000 listings to about 500 on this ID. And when on another ID, supplies of my most popular product dried up temporarily, again, nothing else was selling either. I am confident I will be back in the game by January when we are settled in to our new home, but it was a surprise.
