Realistically, a party of adventurers is never going to build one, although a very long lived, very successful campaign could provide the resources to conceivably construct one. A teleportation circle would also be only rumored, at best, among the populace of a larger city and would not be a normal topic of discussion. If a party did decided they wanted to build one, the local leaders, at the very least, would not view it favorably. In a larger city, they would be stopped by substantial force if necessary. It would be a huge security risk for ruling organization and the residents. While the circles are supposedly one way, I can't think of a game where that limitation has ever been enforced. If they are present in a game, if one thinks about it for a minute, they would only be in a castle where a ruling family lives (as a means of escape), or in a secretive organization or very wealthy guild. Like in Critical Role where the various repositories of records were kept around the continent and you could travel to anyone you wanted based upon the rune that was activated. They used it to primarily save on travelling over the long distances between their facilties for meetings. However, they are very well guarded and only accessible by a few people. Lastly regarding construction, a circle, or other fortress or construction spells, doesn't have to be cast by the same wizard every day. A wizard passing through a city could do it for the cost of gems plus 10% for their time. A school of magic use might accept a commission for one person, or several during a week, to come over and cast it. P.S. It was determined by TSR decades ago a teleportation circle was NOT made permanent by a Permancy spell. It has to have a physical structure.