Because of the beading and embroidery, unfortunately a lot. It looks like close to 200 pearls plus a lot of gold embroidery. I can use fake pearls (although why bother when I can get freshwater for $2 a strand?) and just machine sew on gold bands but that a)wouldn't look as nice and b)you still wouldn't get the gold embroider around the bodice.
For the fabric it would depend on what you want. Linen or twill is easier to work with (for me) than most silks or velvets. So linen would be slightly less and twill would be the cheapest. For the skirt, bodice, sleeves, and chemise, out of twill I'd gauge around $350. That's mostly because of the odd shapes in the gown.