Do people get subs merely for profit?

Sorry if this isn't allowed. as it's just general opinion/discussion, but I belong to a couple of fb groups focused around selling/swapping Boxycharm items (and other subs but mainly BC) and I notice a lot of the time some people seem to be selling every single item, for more than the price of the actual item but less than the cost of the box(per group rules.) Sometimes even selling one item for the price of the entire sub itself. Maybe this is an obviously well-known practice and I'm just slow, but it seems like they only sub to make money off the items individually. I get if you don't like one or two items or were hoping for a different variation, but when I see them selling every single item every month it's just weird.

Does anyone else find this slightly irritating, or am I just being a busybody? Are they just smart? Seems almost like taking advantage of people somehow. Idk.