Going to x2 what Trixie said, with a caveat.
Now, say, someone gets injured in the Dunes in the vicinity of Nippur and wants to use your medbay, you can charge them (I'm okay with that, much like it's okay to pay people for 'faction quests' or for factions to set up bounties). After all, you're offering them a tangible IC benefit, which might be helpful for someone in case they think they're going to get hit again (Pennywise's situation and what Seventeen endured last summer come to mind as prime examples). Bear in mind, that prime you let in and charge to heal could also get fully healed and proceed to attack your vault, as they'd already be inside your Base/Fortification.
edit -- you cannot charge for base services unless there is a tangible need, like any other exchange of OM between players
Now, say, someone gets injured in the Dunes in the vicinity of Nippur and wants to use your medbay, you can charge them (I'm okay with that, much like it's okay to pay people for 'faction quests' or for factions to set up bounties). After all, you're offering them a tangible IC benefit, which might be helpful for someone in case they think they're going to get hit again (Pennywise's situation and what Seventeen endured last summer come to mind as prime examples). Bear in mind, that prime you let in and charge to heal could also get fully healed and proceed to attack your vault, as they'd already be inside your Base/Fortification.
edit -- you cannot charge for base services unless there is a tangible need, like any other exchange of OM between players