4 yards @ $1/yd 1.9 ripstop nylon from the now defunct Wally's World $1 bin.
Tie an overhand knot in each end.
Pack (2) of 15' boat tie down straps from local auto parts store. In the discontinued bin. $10. Cut off the cam buckles. Tie bowline knot in one end. Form a slip loop with the bowline and put it over the fabric knot. Pull it tight. Use a Speer style wrap with the free end around the tree (takes a lot more time to get the adjustment just right, but it will hold.)
10' x 8' piece of Tyvek from a new home construction project. Using sign language you can probably get it from a worker very cheap, or a supervisor on the project will let you have it for modest costs. (For a scout troop you could get a roll of Tyvek, from Home Depot, cut it up, and share the costs. ??? $100 for 100' x 8'???)
Spool of "real" mason's line... ~$10 for 500 feet or some crazy numbers like these. Cut 10' lengths of line. Make a slip knot. Fold a small rock into the Tyvek in the middle of the short edge, loop a slip knot over the rock/Tyvek, tie to tree. Repeat on the other side. Fold a small rock into each corner of the tarp, slip knot, stake the corners down with tent pegs from the tent you used to use.
Thermarest pad from my ground days. Sleeping bag from my ground days.
Bug dope in a bottle.
This was my actual system for 2, five night trips in the beginning. ~$25.
... Because I was too cheap to splurge on a $100+ Hennessey. (Don't even ask how much I have invested in this hobby now....)
8 yards of dark Tulle from the $1 bin can be "creatively" held together to make an envelope for a bug net. Did that for another multi night trip until I created my 4-in-1 sock that is posted somewhere on this forum.
Call it a pound each for the hammock, the webs, and the tarp: ~ 3 pounds. Hammock and webbing pack really small. Tyvek is a witch to pack! but it is pretty light weight.