Nice gear cost Money.....
Cuben Fiber is not cheap ... thats why it cost so much if paying $300+ for a tarp is not for you... don't ..get a Silnylon tarp there are many nice ones out there and are around $100 that will work just fine
Cuben Fiber is around $25-30 a yard keep that in mind when asking why they cost so much(11x10 tarp would require 8-9 yards or fabric thats $200-280 depending on how much is needed and cost of fabric itself)
Tarps like HG's are glued as well.. so think of the cost of the other material involved in making one and time
also as said it weighs a lot less than Silnylon and packs down smaller
like anything new it will cost more untill the price of the Fabric itself goes down
Zpack makes a Hammock Cuben fiber tarp for $235 thats the cheapest one out there and is really nice (i have one) well worth the money IF you backpack .
if you car camp more i would say get a Silnylon tarp unless you have the extra money for the Cuben tarp and must have one