I bid on a power supply for my old computer 5 days ago.

When I bid on it, my bid of $10 was the first bid and there was 5 days left to buy the item.

Until 1 hr ago, my bid of $10 was the highest and no one else has bid on it.

Now I get an email saying someone else has bid on it.

I go look and the bid is now $11.

So I bid $11.50.

Well, $11.50 is not high enough - whoever this other person is, he has an automatic bidding system (which I have NO idea how to do) and he is beating me by 50 cents after each time I place a bid.

So now it's at $15 and that person is the highest bidder.

I don't know how much higher is his automatic bidding going to take it.

How do I know this person that's bidding on it is NOT the seller who created a separate account so he can jack up the final sales price by bidding on his own item?