I'm running a 5e Eberron campaign. My players are about to discover that Lhesh Haruuc is secretly building a lightning rail line from Rhukaan Draal towards Sterngate, aided by a rogue scion of House Orien. In this campaign, slavery is legal in all of Darguun (contra the statement on pg. 112 of the official 5e campaign setting). As a result, other nations and dragonmarked houses are extremely reluctant to deal with Darguun: think anti-apartheid divestment. So Haruuc is funding this project himself, with assistance from his collaborator from House Orien and his own slave labor.
I want to determine, realistically, how quickly this line could be built. Haruuc thinks greed will take over once he connects to existing rail lines, and that House Orien will start sending trains to Darguun. So he isn't building trains; he's only identifying the best route, grading it, and installing conductor stones. The big unknown here is the conductor stones:
- How much does the raw material for a conductor stone cost?
- What level of magical ability is needed to manufacture a conductor stone, and how long does the process take?
A conductor stone is clearly a magic item of some kind, but it's not clear to me what its rarity is. This post indicates that in some previous edition the conductor stone was described as an air elemental bound in a Khyber dragonshard; however, I can't find any explicit statement to this effect in the 5e book. Pg. 235 describes the conductor stones but implies that they're distinct from whatever holds the bound elemental:
Each cart…has a conductor stone embedded in its underside. A
corresponding set of conductor stones laid out in a line on the
ground interacts with the stones in the carts to form a rail for the
train to follow. Lightning arcs between the two sets of stones,
accounting for the system's name.The elemental vessel at the front of the train, called a crew cart,
holds a bound air elemental that propels the train along its route…
Similarly pg. 275 states that air elementals bound in Khyber dragonshards are the basis for the lightning rail, but doesn't mention conductor stones.
This old post asks about the price of conductor stones, but it seems to be asking about finished stones, not the raw materials or the labor required. (And the discussion didn't reach a conclusion anyway.)
I'm not interested the mechanics of the actual procedure for creating a conductor stone; my characters probably won't be doing this. (If they do, I can use the suggestions in these answers for inspiration.) Rather, I want to get a sense of how the process scales up. I'm happy to assume that Haruuc has enslaved high-level magic users (including gnomes, if necessary for elemental binding) and/or skilled artisans from House Cannith. If I can get a sense of how much gold the raw materials for one conductor stone would cost, and how many person-hours are required to create one, I can extrapolate costs per mile of the lighting rail line.
Best Answer
This is up to you
The short answer is that I think creating such a conductor stone would likely cost about 50 gp and take about 5 days of work in a 5e framework. But you as a DM have total liberty to set the cost to fit your narrative.
Technical answer
For a technical answer, the magic item rules on page 281 state that:
The Orien trains are described to have lightning arcs between the carts and the conductor stones that make up the rail. With the carts being 60 feet long there must be at least one conductor stone per 60 feet, or about 90 such stones per mile, maybe more (based on artwork and earlier editions, you would need a stone every five feet, or over 1,000 stones per mile - credits to GMJoe for the info).
Considering that the lines extend for hundreds and thousands of miles, the system needs many hundred thousands of these stones. That sounds like these should be common magic items:
Without dragonshards, according to XGtE p. 129, crafting a common magic item costs 50 gp, and will take a workweek of 5 days. (Based on the DMG p. 129, the cost would be 100 gp, and take you 4 days of 25 gp increments; consensus is that the pricing in the DMG is high, which is why the XGtE optional rules lowered it).
With dragonshards, there is a simpler process to create such items:
The price given for a common magic item that is not a spell scroll or potion of healing is:
* Halved for a consumable item like a potion or scroll
Based on this, the price should be 50 gp. At over a 1,000 stones per mile, the cost of one mile of track would be above 50,000 gp.
Economic answer
Your question is about economy, and the lighting rail is effectively a railway system. Another way to look at this is: what can one mile of track cost for this to make economic sense?
We can try and estimate this from translating the cost of real world railway systems, which need to be economically feasible too. Using rough numbers, in modern times, the estimated cost for new rail construction is about $1.5M per mile.
Because it is hard to translate between USD and gp, we'll use the value of a year of work of an unskilled worker as a conversion factor. An unskilled worker salary is about $25,000, so one mile should cost about 60 annual salaries. The annual salary of an unskilled hireling in the game is 2 sp/day, or about 73 gp per year. This would mean the cost of one mile of track should be 60 x 73 gp or about 4,380 gp.
If we assume one mile has 90 conductor stones, the price per stone would come out to about 48gp, very close to the 50 gp for a common magic item, which takes about 32 hours to construct.
If we assume over 1,000 stones per mile, then using this comparison, one stone only could cost about 5 gp, which seems very low; so construction would need to cost more than for a mundane railway track, and riding the train would need to be more dear, too. This is borne out: E:RftLW does not give costs for tickets, but Wayfinder's Guide to Eberron, also for 5e and by the setting's author Keith Barker, gives this pricing
The ticket costs about a week to a month of laborer wages. This is several times more expensive than a long distance railway ticket today, if not a tenfold increase then maybe three to five times. Based on this, the price to a stone could be in the range of 15 to 25 gp.
Narrative answer
While I can understand your desire to find a price for this, I do think that you are spending your time on the wrong thing.
What are the overall costs house Orien has for maintenance of infrastructure and seats of power, paying retainers, fielding armies? What is their income from operating their train network, tithes, mines and trade levies? A single number in isolation is meaningless here. Would 5,000 gp/mile be much for them? Would it be little? How about 50,000 gp?
The thing is, it does not matter. You do not need to know this for your narrative to work. They are building this rail, they are using slaves, they are indenturing gnome artificers, it's all many thousands of gps, a huge undertaking. That is the cool stuff and all you need for the narrative setup. Your players will not write a doctoral thesis on the economic margins of freight transport, and likely have little interest in it.