How do I cost out a homebew magic item: Mutex Bag Of Holding?

Question

For the Pathfinder RPG, the costs and limits of a Bag of Holding are defined pretty clearly. Though it comes in four different types, I'll take a Type I Bag of Holding as an example. The Type I bag weighs 15 pounds, has a Contents Limit of 250 pounds., a Contents Volume Limit of 30 cubic feet, a Market Price of 2,500 gp, and a Cost To Create of 1,250 gp. The creator needs the Craft Wondrous Item feat and the spell Secret Chest. Caster Level is 9. The bag of holding opens into a nondimensional space.

For my campaign I've created a Mutex Bag of Holding. A Type I Mutex Bag of Holding is actually two different bags (A and B). Both bags open on to the same nondimensional space. Only one bag may be open at a time. If Bag A is already open, Bag B refuses to open and cannot be opened.

The advantage here is that Bag A can be across the globe from Bag B; it provides a way of resupplying a party from across vast distances, passing notes or potions or rations or whatever. Picking up and holding the bag does not provide any sort of identification, location nor communication with the owner of the other bag, but there's aways Sending spells. Passing notes through the bag is permitted.

EDIT In case it is relevant, the Player Characters in my campaign currently have only one of the two bags and don't know who possesses the other bag: friend, foe, or absent-minded wizard who left Bag B open.

Does something like this already exist? I have not found it in my searches to date.

How do I figure out the Cost To Create for this item? I treat the two bags as one set. I plan to put a premium on this because the pair allows some new creative uses over a single Bag, but I'm not sure how to cost this out, as it approaches the convenience of a Teleportation Circle that is both permanent and portable.

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Answer 1

The ring gates are close to the item described:

These always come in pairs—two iron rings, each about 18 inches in diameter. The rings must be on the same plane of existence and within 100 miles of each other to function. Whatever is put through one ring comes out the other, and up to 100 pounds of material can be transferred each day. (Objects only partially pushed through and then retracted do not count.) This useful device allows for instantaneous transport of items or messages, and even attacks. A character can reach through to grab things near the other ring, or even stab a weapon through if so desired. Alternatively, a character could stick his head through to look around. A spellcaster could even cast a spell through a ring gate. A Small character can make a DC 13 Escape Artist check to slip through. Creatures of Tiny, Diminutive, or Fine size can pass through easily. Each ring has an “entry side” and an “exit side,” both marked with appropriate symbols.

Normally, I wouldn't quote the entire description, but I wanted to demonstrate the extreme limits placed on this item compared to the item the question describes. And the ring gates cost 20,000 for a pair.

This GM wouldn't allow into his campaign a magic item exactly like the one the question describes. It's a world-changer, and maintaining verisimilitude after its introduction will be challenging unless the campaign's designed around it. This GM humbly recommends a per-day insert/extract weight limit similar to that of the ring gates equal to the bag's typical capacity. Were that limitation added, a price of 10× the normal cost of a bag of holding of the same capacity may be reasonable. Absent that limitation, however, and this at least borders on a minor artifact as wide reproduction of such items obviates entire industries.

Answer 2

So, it sounds like this works exactly like two different wizards using the same target for secret chest. I would cost it like two spells, at will. That's 2x(9x5x50), plus 5000 for the focus (not doubled). That's 9500, so maybe bump the minimum CL to 10, which moves the price up to 10,000 gold and gives it an even 10 cubic feet.

Wizards already have this in a non-permanent way just by wanting it, so you may as well let non-casters have nice things too.

Answer 3

There are two questions here. One question is : how much should it cost to create this item? The other is: how much can you sell one half of it for?

This item could be used for two-way trade between two cities, so we might estimate its cost as similar to that of two permanent teleportation circles -- so, 47000gp. The teleportation circles are fixed to one place, but they have higher throughput than the bag, so maybe it balances out.

However, one half of the item is basically useless: it's like a normal bag of holding except someone can steal your stuff. No NPC should be willing to buy this.

I assume you're planning to use this as a plot trigger: the npc tries to buy the bag, and one or both sides potentially try to backstab the other?