1) Who mines the metals used for coins, especially among cultures like the L'Arile Nation or the Elves and how do these materials end up spread among the mechdoms and cities?
2) Who the heck carts around hundreds of pounds of gold--or even platinum, in same cases--to pay for mech construction? Hypothetically, you should be able to pay labor costs by giving the workers two hot meals a day and attract the gimlet eye of a supervising coglayer by offering him plans to something interestingly mechanical. Or maybe just a pile of parts and a couple of barrels of grease.
I've given more thought than is probably healthy to how the economy of Highpoint functions. So...
1) Much of the metal in this setting is recycled - it's pre-lunar metal that's been reused. This is where a lot of the smaller metal items like coins come from. The L'arile Nation is more inclined to use wooden coins, ceramic coins, or coins made of easily-found metals like brass. We haven't presented an elaborate multinational coinage system for DragonMech, as a lot of roleplayers seem happy with the standard d20 four-metal decimal coinage system. But it's there in the back of my mind.
Two mechdoms do substantial mining still, the Legion and the Stenians. And the inhabitants of the subterranean world aren't hampered by the lunar rain, so one of their biggest trade items is metal.
2) Exactly - who would
use gold for that? The gold cost of a mech isn't a matter of a straight fee - it represents the overall construction cost. Workers need to be fed, clothed, sheltered from the lunar rain, and defended from hostiles. That costs money. The mechdoms don't transport tons of coins around when they can just send the goods directly. Now, if you're a smaller operation, you might find yourself needing that big pile of money to pay for it. Or you could trade for equivalent services, or you could barter with fancy steamtech or weird magic or lunar hides, or maybe you use lies and threats... you've got options.
3) Unlike most fantasy settings, Highpoint has never had many large aboveground nations, which means it hasn't developed intricate or reliable coinage systems until recently. Pre-lunar Highpoint was very nomadic, and therefore its economy was largely one of barter. Even now, the Stenians and the Legion are the only mechdoms that would really be inclined to coinage. The L'arile would barter goods or trade services, the orcs/brigands would steal and raid, the Irontooth would do all of the above. So if we were trying to make the setting more realistic (given the context of steam-driven mechs hitting lunar dragons with axes), we'd have a complex economic model driven by 8-12 regional power centers with different resources, social models, etc. I'm a world-builder by nature, so I love that kind of thing. But a lot of people would rather drive their steam-driven mech around and hit lunar dragons with axes, not worrying about whether the economy is plausible. Nothing wrong with that. So we have the default d20 economy there for the majority of people to use without questioning, and if anyone wants to try and develop something more intricate, we have a message board.
I can understand that. It just occurred to me that for a lot of people in Highpoint, life exists on a complex web of debts and favors. If you're a coglayer, you do work and the occasional favor for the area you're in, and once people know your name, they might be willing to float you a few tons of steel and start asking the folks back home in Duerok if they can snatch up all the adamantine they can get their hands on--and of course, now you'll owe a favor, a big one, to the person who acquired your raw materials for you, so next year when he wants to get a big cargo to Edge, you'll of course be obligated to make the three trips from his underground mine/shop to the city of Edge, and encounter a lot of headaches each time you do it.
Money exists...well, because people have gotten the idea that metal coins are worth something, but it's more like platinum, gold, silver, and copper are just another commodity that people trade around, or like a voucher that says, "Good for anything, as long as you have enough."
I forgot another part of that essay. It suggested that you actually can't buy
magic items worth more than, oh, 15,000 gp or so. You can get a major magic item out of love, or blackmail, or spoils of war, but not for money.
I can't tell if I'm making sense here, or just rambling, but I can tell a few things:
1) The Favor Economy probably has a large influence in Edge, what with all the power blocs maneuvering around each other and making concessions.
2) It might be nice to work up some sort of "Twenty/Thirty/Fourty Ways to Trade Favors" as as a sort of list of plothooks for people who like this sort of thing (inspired by the last section of the Last City, of course. :loved reading that: I might work on that, to give us something fresh around here...)
3) Just the players accepting that they could participate in the Favor Economy could set up a decently episodic set of adventures where the characters are engaging in what might be called Commerce, where the reward for completion might be a conditional promise of future aid rather than a magic axe.