The concept is to shop your stash first and if you need something for a project you really are going to do, then is ok to buy. Sometimes you just need that one more thing, or just gotta do what you gotta do!
For an actual business transaction, I don't see any need for any exemptions at all. The problem some of us get into is the potential of the fabric and the desire to acquire. Oh sure, "some of us" is me
As someone who was once in the running for "she with most fabric", I still maintain there is nothing wrong in collecting fabric but I have decided to reduce my fabric load. I have to stop bringing fabric in (but i have a terrible lack of self control at $1/yard) and I have to either use the remainders or find people who will. I have greatly reduced my stash by giving and now am mostly in the using mode.
Still haven't ordered my yellow. The box of fabric I sent arrived very quickly! Expecting my dragonfly back to show up Monday, hoping to bring it to show the ladies on Tuesday. We (the Tuesday group) are progressing on the comfort quilt project, I need to get off the computer and back to the cutting table. But in my defense, I have provided and prewashed fabric from my stash -- one piece for the sashing was dated on the selvedge as 1993 -- and I remember buying it! Terrible thing my memory. The other piece I found at the Goodwill a couple of years ago is a perfect border. And -- I get to take the back out of my stash too!