composite skins vs ply for ultralight

Was just looking at 1/32" ply prices vs carbon fiber. Seems like carbon fiber that was as stiff in bending would be cheaper, though something lighter in between two layers would be needed to make it lighter for the stiffness. I neglected the price of the epoxy, because I figured that would be a small fraction of the expense. Furthermore, the CF is MUCH stiffer in shear, which could be pretty useful for a wing d-tube. For instance, the shear modulus numbers I found were, in the 0-90 degree case, around 0.8 GPa for birch and around 5 GPa for cloth. For +/-45 degrees, 3.3 and 33 respectively. The numbers I've found also indicate that +/-45 uni isn't very much stiffer in shear than +/-45 cloth. Does this all sound right? I did some very rough calculations which seem to indicate that for an ultralight glider, you really don't have to worry about wing twist from pitching moments at high speed when using carbon on the bias. That opens up some options if trim drag doesn't turn out to be a big problem.

From Wickes, I got that 1/32" ply was a bit under $wrong/square foot. $2!

From Soller composites, one can get, say, 11 oz. carbon fabric for about $1.40/square foot! Double layers would be somewhat more expensive, plus there are biaxial and triaxial options, etc. wrong sentence deleted. Some of the options really need a cheap, light core, though.

I don't know how, when overlaps are necessary, one is supposed to prevent bumps. Might be a problem if using 0-90 weave on the bias.

Anyway, am I just looking at the wrong plywood suppliers or is it really true that carbon is cheaper???