This web was made for under $20 and it's entirely woven out of common clothesline style rope. It's about 20 feet high and maybe 12 feet along the base. It's easy to make; it only take a little time. I think it took me about four hours but the results are totally worth it. I've gotten lots of great comments about it.
Rope - I used five 100' lengths. This inexpensive rope is sometimes marked as intended for clotheslines. I cut two of them into 25' lenghts for the perimeter and the three cross ropes. At Walmart the other day I saw 100' lengths of rope for something like $2.64 each. <UPDATE: Harbor Freight sells clothesline for $2.99, item #66565.> If your web is truly humongous (awesome!) you might need more rope.
Rebar - Two 2 foot pieces of 3/8 inch rebar. I got it at Home Depot for under a dollar each. I bent the end into a hook with my vice to make it easier to attach the rope.
Eyebolt - Just a simple eyebolt. The one I had on hand was pretty heavy duty, maybe 4 inches long. I forget what I paid for it at Home Depot years ago but surely it's under $5.