1.75 .120 runs 2lbs/ft, and the DOM I have priced locally runs $6-8/ft. It will be unlikely to build the cages you want to out of DOM given the amounts you want to spend.
Unless someone here has done several identical cages, it is unlikely anyone has written down the exact amounts. I know my buddies that have built cages just buy 4-5 20' sections to start with, then buy more if needed. Not exactly the smartest way when buying material, but most have more money than patience, and figure they will find a use for any of the leftovers.
If you are trying to get an idea of how much tube is needed, you could tape out the design of the exo-cage on the Runner, and for the internal cage 1/8" round bar should work. That should get you a ball park amount, then round up to the nearest 10' or 20' section for a buffer.