As a datapoint, I usually buy caffeine in 500g tubs for mixing purposes.
Note that I don't ingest the stuff myself; I'm way too sensitive to the effects. If I drink regular coffee, I'm fighting with my customers all day, which isn't good for business, not to mention the irregular heartbeat. Sometimes I wish I could use the stuff; it's helpful e.g. to not fall asleep driving.
(We use it to make caffeine suppositories for fast days. Much more pleasant when inserted than using ground-up NoDoz tablets.)