This is just a battle of desire vs. cost. Is it something that will come up again next week if you miss on both auctions? Can you wait until next week? If yes, I'd take my chances here, secure in the knowledge another "thing" will be along soon. If it's an item that's expensive, but the BIN is fair, I'd probably just purchase it and rationalize that if I need the money back, I can sell it down the road for what I paid (minus shipping/fees).

If it's an uncommon item...and you need it...I'd just buy it and be done. If you pay 10% more, it's not the end of the world. You can always make that money back on another flip.