Last second changes and at work, there are departments that are notorious for doing this.
We did a 400 person breakfast catering. Nothing fancy, just a croissant per person, coffee and tea, and about 25 cases of water. After delivering, we needed an extra coffee pot for another 100, extra 100 croissants that we couldn't get now because we ordered them, and another 5 cases of water. This was all an outside catering and the taxi bill came up higher then what the client was willing to pay. On top of that, they had the audacity to ask if we could give them a break on the cost of the croissants. Again, it was ordered from a supplier since we couldn't handle such large numbers and what we charged them was what we paid for them. Anyone got a 4" long rope with a noose on the end?