I guess you are looking at the 10foot Blackbird 1.7 DL to have the 400b rating and under a kilo. As Simon says ( "Simon Says" tee hee

) this is 2 layers of 70d at 880 grams with whopies or 964 grams with buckles and straps. Plus a little extra for 2 carabiners, or whatever you use at the tree. $185 whoopee or $175 buckle and strap
The comparable HH is the Expedition, with 200d Oxford nylon, which in my opinion is a nicer feel to lie on, and will hold its own strength wise with 2 layers of 70d. If you click on the customise button for the Expedition, you'll see that the hammock on its own weighs in at 952gm for the zip model, or 907gm for the classic, with no need for 'biners etc. $120 zip and $100 classic.