Do you mean cost to print or cost of cast metal. I use .9 times the weight of the cured model to determine metal needed.
Weight of print x .9 = approx. weight in wax*
Weight in wax x S.G. of metal to be used = metal weight of cast print (does not include sprues or button).
Just if u needed to know.
*The resin is approx. 1.1 times heavier than water (10%). S.G. of casting wax and water is 1.0
Dance like nobody's watching!