A permanent teleportation circle costs around 18250 gold pieces to make (50gp material cost x 365 days in a year), which is quite a lot to setup. But once the teleportation circle is permanently there, how much should whoever setup the circle charge for it's use?
Recoup one day of the permanent casting per group, at least, so 50 gp for starters. Assume opportunity cost (foregone work/commissions) doubles that to 100 gp. If you can safely say you're sparing each traveler cost of rations/feed, and assume a 100 mile journey, that's maybe 55 gp of savings, so you could have that as a per traveler add on...
100 gp + 55 gp per traveler
Remember that, if you're going by the
teleportation circle spell, a permanent circle is not a portal. The benefit of the permanent circle is twofold:
(1) When casting
teleportation circle there's no need to inscribe the circle. What does that mean? Well in typical 5e fashion the rules are silent. My ruling was that a permanent circle means that (a)
teleportation circle can be cast within it as an Action instead of 1 Minute, and (b) the 50 gp of rare inks isn't required to be expended.
(2) The permanent circle acts as a RECEIVING site for a
teleportation circle spell cast elsewhere in the world.
So you also have the cost of the 5th level spell to actually cast
teleportation circle, assuming no PC can cast it. This is going to be high. We have an estimate from Tyranny of Dragons that a 5th level
raise dead costs 1,250 gp. Then if we deduct the 500 gp diamond that's consumed we get 750 gp... Again, this is just from one D&D book, so take with a grain of salt and adjust as needed.
100 gp + 55 gp per traveler to access the circle
If a spellcaster casting
teleportation circle is required (probably yes), then add 750 gp
This assumes the Sigil Sequence to the destination is available/unrestricted.
So a 4-person party of <9th level (i.e. without their own access to the 5th-level
teleportation circle spell) might pay 1,070 gp.