This happens more often than it should. More often that not, I think it is a result poor communications between the carrier and the shipper, or their agents.
We've been dispatched on a B load that weighed 4200 pounds and many that have exceeded the agreed upon weights for a van. We've arrived at the shipper and been met with as many as six skids, quite often three skids or equivalent. Sadly, our usual consolation by the carrier's agent is a curt "This is a dry run; your pay is $51.04"