A yard is very close to a ton usually they use ton cost on products that don't change much when wet like rock. Yards are usually used when the product weighs more when wet like dirt mulch sand etc. I have seen some smaller rock yards have sized buckets on the loaders and no scale so they will sell by the yard. Yes that 150 # is a pain but when your bidding commercial thats the # you have to use to be competitive. Makes a big difference when you are bidding 100's of tons of granite. I agree with you, when doing residential I go about 100-125 per ton depending on rock size. Thank god I'm not in that commercial rat race any more.