If you look carefully at the material on the Primus Express Lander you will find that the 6 ounce figure is for the stove unit only. With the pump and pressure fuel bottle the assembly will be closer to 15 ounces.

I looked at the Lander for use on a JMT hike this summer and discovered the listed weight did not include the pump assembly nor the relatively heavy fuel bottle. The stove won't work without both. I thought, at the time, that neglecting to mention this little fact was disingenuous, at best, and more likely deceptive.