Conspire with Other Buyers.

You might not have thought of this, but if there are two auctions for the same item and only you and one other buyer are bidding, why not get together and work out a ‘you take this one and I’ll take that one’ deal? This avoids you raising the price on both auctions just to get one each. If you make a few friends, you can even work together on auctions long-term, taking it in turns to bid.