Thats an excellent question. Adding to the confusion? You may be carrying extra stakes or a ground cover, and that can add weight. Plus, lets face it, I dont think every tent made by a maker is the same weight. Odds are good that they sample a batch, find the lightest, and use that as packaged weight.
The GoLite Utopia 2 ($275) is pretty much the lightest tent out there. Its a real tenttent poles, silicon-impregnated flybut has no inner wall (its a single-wall tent) and no floor. Still, if you can live with that, for two pounds, ten ounces (packed weight, two pounds, seven ounces minimum weight) you have a tent.
I admit, I dont find that kind of setup real practicalId be carrying a floor liner and adding a pound, just to keep my pad and bag off the ground.
So...I have thought this for a long time, and still think it. The lightest practical two-person tent is in my view the Sierra Designs Clip Flashlight 2 ($199). Three pounds, six ounces ("trail weight"no packaging or anything). It achieves this with a tunnel-tent design that requires you to stake it out. But that saves you a pole or two. Add light materials, and you have a light tent.
A worthy competitor is the REI Quarter Dome 2 ($270). A free-standing tent that comes in at three pounds, 12 ounces, which is pretty remarkable.
My own favorite is the Black Diamond Lighthouse ($430) a free-standing, single-wall tent with a floor that weighs about the same as the Clip Flashlight, give or take an ounce. Costs more, true. But it's a tough, versatile, practical tent. I use mine for solo camping, as well as climbing trips with a friend.