Based on the thread so far there seem to be some common issues that a new buyer needs to consider.
1. Be sure that the manufacturer's specs actually apply to your camper and include the weight of accessories, upgrades, etc.
2. Add weight for any mods needed for your truck such as supersprings, airbags, tiedown mounts, fastguns, bedliner, blocks needed for lift the camper, leveling blocks, etc. These are likely to total at least 300# and can be considerably more.
3. Include any accessories you add such as mattress upgrades, extra battery, solar and/or generator, extension cords (I carry a 100' 12 gauge, 3 wire which is really heavy), air compressor, BBQ grill, tools, hardware/supplies, dump hose, water hose.
4. Add in roughly 1000# for personal items. That may sound high but a lot is included: food (really heavy if you stock for many days or extended use), bottled drinks, pots/pans/plates/etc, clothing, extra boots, bedding, and small personal items such as cameras, laptops and the like. If your personal items include anything unusual or heavy add extra for those items.
You are likely to find that if you add the weights for the truck, passengers, and wet weight for your actual camper, you will be about 2000# short of the actual weight. Roughly 1000# will be for items 2 and 3 above and another 1000# for item 4. It all adds up in a hurry.