These sites are like gambling. It seems too good to be true, and that suspicion is well founded.
If you don't know how these sites work this is how:
It's an auction set up with no hard ending (as long as people are bidding, the auction won't end)
Each time you bid the price of the item goes up by .01$; but you have to pay to bid. The amount you pay to bid ranges, but let's say it is .50$. It sounds inexpensive, but let's examine a hypothetical. A TV that sells for 25$, how much did the TV actually sell for? The 25$ indicate that here were 2500 bids @ .50$ a piece is a total cost of 1250 + 25 = 1275$ Definitely not a deal.
I say it's gambling because each time you bid it adds time to the auction. And you're betting your money that you will end up with the item. What this system does is spreads around the cost of the item among all those gambling to win it. Personally I would make one of these sites if I had the money it's seems amazingly profitable.