Hi,
So the minimum bid is equal to the current price.
If the two maximum bids are 900 and 1000, the current price the winner will pay is 900. 1000 is actually the maximum amount the user would be willing to pay.
So if someone then enters 950, the winner at 1000 would now have to pay 950.
And if someone enters 1050, he becomes the winner and would have to pay between 1000 and 1050.
That's a way auction sites handle bids when bids are not known by others.
I can see that you've displayed the auction history on the product page. In that case, it's indeed strange because everyone can see the maximum amount the potential winner is willing to go to.
I suppose that in that case, the amount bid by the potential winner should be hidden in the public history.
You might want to switch the "auction mode" to "English auctions" so that the winner pay the highest bid.