Here is an idea call a scrap yard ask to talk to someone in the non ferrous department about pallets and skids and ask them how much on average do they happen to weight? They should be able to tell you an average. My guess would be 75 to 80 lbs. Most of the gaylords I have ever seen are thick walled. Heck most of them are from alan shulman or some company like that that deals in plastics and resins. That is when you know you have loaded way to many boxes with scrap when you can remember that.