How do people make a profit on eBay?

I have been looking for days now. I look on eBay at people selling Brand new 30 GB video iPods for $270 and even lower. I have yet to see a price to purchase and resell come close to that.
I have sold some goods around my house to get a start on eBay and I'm looking for a supplier for other things. Though you just can't possibly compete with those prices if they are selling them for lower than you can buy them for.
I was looking to possibly getting into the authentic and replica sports jerseys because they would be easy to ship and they are good sellers. But yet again I can't figure out how they sell them that low. It's kind of making me angry.
I came here to Salehoo hoping this would help, but again, no luck. Prices for stuff are terrible and profit is nearly impossible for most items. Anybody knows of a supplier for sports jersey for decent prices? Please help, any insight is appreciated. HOW DO PEOPLE DO IT?

What are they charging on shipping? They could be making their profit off of shipping. We've got them on our website for $276 each with no minimum. A lot of times sellers will buy large quantities of items. Lets say they buy 100 of these and sell them all for cost but make $5.00 a piece on shipping. That's $500.00.

I AGREE WITH DIRECT CONSUMER.

Do not look at how people make profit. Find what you wanna sell. It's better to fulfill all our promises than to offer big things that we can't keep.

I see you want to make profit on ebay. I will help you out. Let me give you some advice. Making profit on ebay is very hard due to the seller fees you have to pay and the listing fees and paypal fees. I would not recommend selling any electronics because they are the least profitable. Clothing is your best option because it is easy to ship and is cheaper to buy.