I think Chatter has hit the nail on the head - the bids that arrive after yours are higher than yours because the bidder has a better idea of what the item is worth - to win you need to research and place a snipe that's at the highest you want to spend and not worry about lead times. Remember sniping only prevents a bidding war, it doesn't guarantee a win.
All together now...
It's not the last bid that wins, it's the highest!
R2 (all clichéd out!)