How would one create a bag of coin-changing?

Question

I was chatting with a friend about Dungeons and Dragons, and he had mentioned that in 4th edition, there is an item that converts coins to different denominations. In the campaign that I am running, the players are carrying around quite a bit of copper and silver, and it would be useful for such an item to exist.

I was trying to price out such an item using the Bag of Holding as an example, but it only lead to further confusion.

From what I could gather from the item creation rules, the cost should be

(Spell Level) * (Caster Level) * 2000gp * (Factor based on spell duration)

...For being a use-activated / continuous item. The closest spells I could find were Major Creation and Fabricate, but even optimistically that would put the cost at something like 90000gp!

How would one create a bag of coin-changing, and how much would it cost?

Answer 1

The main difficulty you're having in using the formula is that there is no existing spell that models the effect you want. Both Major Creation and Fabricate are dramatically more powerful than the effect you want in that they can create almost anything. Placing the limitation of converting coins of one type into another type of precisely equal value is a huge limiting factor.

For my part, I would put "convert currency" at a pretty low spell level (0 - 2). This is because I don't typically play campaigns where encumbrance or money changing are relevant... If either of these mechanics ARE relevant to your campaign, adjust accordingly.

Based on that, you'd get a cost more like:

1 * 1 * 2000gp * 2 (bags have no space limitation) = 4,000gp

Which is still probably too expensive to be practical (why not just get another bag of holding to handle the extra coins?)

For a zeroeth level spell:

.5 * 1 * 2000gp * 2 = 2,000gp

... Maybe.

The other way to approach it is fiat: In order to be relevant, the item has to have a cost below a type I bag of holding. Therefore the price has to be somewhere in the 1,000gp to 2,000gp range. So it is.

The problem here is that the formula is balanced on existing, challenge-relevant spell effects. It works much better for an amulet of protection from evil than it does for a minor utility spell. This is why, for example, the Feather Tokens don't have the extremely high costs that come from creating something for nothing.

Answer 2

You should go off of extradimensional-space spells like Rope Trick. Just say that in this case, the extradimensional pocket can be accessed by bankers in Sigil (or somesuch). So you have to wait a few minutes for them to do the transfer, and maybe they'll take a small fee.

Answer 3

The 4e item you're refering to is most likely the Pouch of Platinum^[DDI]:

Property: Normal gemstones and coins of any denomination placed into the pouch are converted to an equal value of platinum pieces. Coins or gems that cannot be evenly converted to platinum pieces are unaffected.

Do you really need to follow the exact item creation rules (as in, CL, spells known, feats, etc.) or was it sufficient if you knew the relative powerlevel of the item to simply say "it costs 1000gp" or something like that? It's been a long time since I dealt with 3e item creation and I'm a bit rusty with it, but I'll try to figure something out.

Another idea: what books do you have? I only have access to the SRD right now but perhaps an appropriate item or spell already exists in some supplement.

Answer 4

I'd treat it as a variant spell of Transmute Metal to Wood. Up it a level or two.

Answer 5

You could base it on the Tech 2 items in the MMORPG Eve Online.

Components needed:
Bag of Holding
3 gold coins of differing type (if in the real world say a dollar, a pound, and a Euro)
A piece of silver chain (links = linking the coinage together)

Resulting item would provide the ability to put coins of one country and get out the coin of the current country (or store your coins in it and they always come out in the local currency), with the restriction that once the bag of holding is changed then it can only hold coins (unlimited number though) and anything in the bag when the spell is cast are lost (the interdimensional space inside was changed so anything in the original is now lost). I would place it as maybe a level 7-9 spell.

Answer 6

Just list it as having a faint or moderate transmutation aura, and just requires the casting of any 2nd (or 3rd) transmutation spell during the crafting. An easy way to handle crafting one, without having to design new spells, or use ones that are unreasonably high.