Player 1: 10
Player 2: 15
Player 3: 20
Player 1: 25
Player 3: out
Player 2: 30
Player 1: 31
Player 2: 32
Player 1: 50
Player 2: 52
Player 1: pass
Player 2: nah - you can have it.
Result: Player 2 wins for 52. If you are gonna bid
several times, we are going to award player 2 the benefit of the doubt that they do know how to put their socks on in the morning and know they are bidding for an upgrade.
I really don't see any other way. They're your DKP folks, spend em how you like. If you want to cockblock a guild member who needs the upgrade more than you, I guess that's life. They should raid more often if they really want it and besides, almost any loot we get we get more than once and generally the price of DKP only goes down.
That's my input on the matter. The closed bidding system was developed the way it was to prevent this exact thing. Open bidding, well, the guild majority voted for it so here ya go =)