Trimec Plus (MSMA) works poorly on crabgrass and requires repeated applications. It turns crabgrass yellow, makes it more noticeable, discolors turf if not precisely applied or too dry and will require 2 follow-up applications this time of the year.
Cost should be based on cost per 1000 sq, not the amount of water you purchase with your product.
bob, your best choice for crabgrass is Drive 75. It costs $2.00/1000, turns crabgrass purple/brown and gives complete control in 1 application with no turfgrass discoloration.
btw: You're required to have your name/phone number on your vehicle when transporting pesticides for commercial use.