Around $450. I did waste some resin, not wanting to run short in the middle of the glassing. Also have cloth left over because it's cheaper when you buy >25 yds. Used 2.25 sheets of 2" thick Dow blue Styrofoam t&g insulation, 2.5 gallons of resin, 14 yards of 6 oz e-cloth, part of 4 pigment tubes, 6 sheets of wet or dry, 1 Goretex vent carrier handle, 1 skeg box, 1 skeg. The board is 9'-6" so materials for a larger board would be proportionally more.
If you have a source for a styrofoam surfboard blank nearby, that would be a much easier way to go. I'm in the boonies here and have no access to actual surfboard foam. The shipping would be prohibitive. Be careful about the foam used. It needs to be closed cell and non-absorbent. The EPS foam will never get saturated even if water eventually gets inside the glass. Some of the other insulation foams are a like a sponge. The blue DOW is minimally dense (not too hard) and must be coated with at least 2 layers of 6 oz. with an extra layer under foot. Surfboard foams are denser and can apparently be coated with as little as 1 layer of 4 oz for a high performance short board. I have not weighed this board (I don't own a scale) but it feels like around 25#.
I would have taken more pix of the stages of building it but being covered in epoxy goo with gloves and mask on is not conducive to holding a camera.