While this report is probably true, it doesn't take into account where the materials are being sourced from (e.g. is the steel from the U.S. or is it from China).  If it's coming from China, you have to factor in the cost of the shipment going to California first (Jones Act).  Then it gets shipped to Hawaii.  If it's made somewhere on the mainland, then you have to transport it over land or flown from wherever it is to California and then it gets shipped to Hawaii.  You also have to factor in the U.S. based company's profit.  You also have to factor in the contractor's cut (mainly because they charge extra for the materials).  This is why I have guesstimated the 40% increase.  It could be higher or lower depending on how many intermediaries are in between the buyer and the original seller.  Oh, and you can't forget the wholesale and retail taxes the state charges here and if the source is on the mainland, you have to pay a tax on the materials there too if there's a sales tax.