As an owner of several campers, I would say you could be getting close to 4000 pounds. Often advertised weights were put out as bare bones campers (we didn't know you really needed jacks or a mattress inside) etc... Many things were optional, and so they were not included in the weight.
Often, owners put mods in too, memory foams, extra shelving and cupboards, new floors over old, roll on roofing, air conditioners... a host of things, and in the end, the original advertised rate is pretty lovely, but not anywhere near reality.
And then, there is the weight when you have filled the propane tanks, and taken on fresh water, but haven't made a dump site yet. There was a great deal on dog food and you really needed several cases of beer too.
3500 - 4000 pounds on board sounds realistic, doesn't it?