See Warbonnetguy's post...
Waterproof 70D (70 Denier) is usually PU coated and weighs about about 1.9 oz/sq yd before coating and 3 oz sq yard with the coating.
$ premium is primarily due to the one copyrighted/patented source for the material, I'm sure.
"only the paranoid survive" - Andy Grove, Intel
Search engines are your friend. Use "Site:hammockforums.net" in your search string.