I worked at a headshop in the late 80's amd early 90's.

We sold nitrous oxide for whipped cream (and to inhale). It's a very short lived high...mebbe a couple of minutes for the average person. It came in 24 packs of nitrous cylinders for about $50 US.

There was a guy who would come in when we opened at 10 AM and buy a case (144 cylinders) for personal use, and be back in the store before 6 PM to buy another case. Eventually over a few weeks he was buying multiple cases every time. His lips started cracking and bleeding from the cold, and then turning blue. We found out he was going to our other stores in the area and finally banned him.

We had people buy crack pipes and other smoking paraphernalia too, but that one haunted me. I had never seen someone fall that hard into addiction, or that fast. He was obviously miserable and could not stop.