You're missing the point of Need Vs. Greed. Need always trumps greed. So if someone is going to use it as an upgrade they should click Need. If no one has a use for the item and everyone clicks Greed, then it goes randomly to the highest roller to sell. So, if you click Greed, there should be no problem, because you won't get it unless no one else has a use for it.
If someone DOES need it and the click greed, well, that's there fault for not clicking the right button, but if the item isn't Bind on Pickup you can always give it to them.
I only pass if I really don't want an item even to vendor.