Magic Item Creation and round usages rules instead of duration

Question

How does one go about creating a magic item with a usage of rounds per day like boots of speed? I haven't been able to locate any magic item creation rules which talks about this, but it makes me wonder if it's related to charges per day and caster level. I can get close to recreating boots of speed, but I am missing something, which makes me wonder if that missing something is what I am looking for.

So boots of speed

As a free action, the wearer of boots of speed can click her heels together, letting her act as though affected by a haste spell for up to 10 rounds each day. The haste effect’s duration need not be consecutive rounds.

Haste is a 3rd level spell and caster level 5. So for crafting it should be a use activation wondrous item for spell level * caster level * 2000 which gives us 3*5*2000=30,000. Now boots of speed cost 12,000, so I need to bring in charges per day.

• 1 charge 30,000/(5/1) = 6,000
• 2 charge 30,000/(5/2) = 12,000
• 3 charge 30,000/(5/3) = 18,000
• 4 charge 30,000/(5/4) = 24,000
• 5 charge 30,000/(5/5) = 30,000

OK, so two charges gives us 10 rounds of haste for the same price as the boots. I could also use a single charge at caster level 10 for the same result but with a better caster level check vs dispel.

So I have recreated the item by cost and number of rounds, but never found anything about making it use rounds instead of a full duration. Since I can see many spells benefiting from this kind of treatment, I feel like there should be rules about it or a cost, but cant find any.

Answer 1

The table that you are referring to is titled Estimating Magic Item Gold Piece Values, not Accurately Calculating By Exact Formula Magic Item Gold Piece Values.

If you refer to the paragraphs above the table, you will see the following:

The correct way to price an item is by comparing its abilities to similar items [...], and only if there are no similar items should you use the pricing formulas to determine an approximate price for the item.

If you are the GM, you can rule that all 'use-per-day' items can be created as 'rounds per day' based on total duration of its listed uses. If you're not the GM, you can try to persuade the GM, using the Boots of Haste as a precedent.

Answer 2

The boots of speed are actually priced as a 1/day effect, but the designer allows the wearer to split the duration between multiple uses, which is a small quirk that is not priced.

If you look at the caster level, it is a 10th CL item, which is exactly the maximum duration of the haste effect, 10 rounds if the user decides to use all the charges.

Take the use-activated effect as base: CL 10 × 3rd spell level × 2,000 = 60,000 gp base cost.

Use-activated or continuous     Spell level x caster level x 2,000 gp

That's the price of what would be continuous, unlimited (probably greater) boots of speed, expensive, but for what it does, that's a fair price.

The core rulebook's boots of speed aren't that great though, as they only work for 10 rounds a day, so to calculate that, we can divide the total by cost by 5, as if the boots had a single charge that lasted 10 rounds.

Charges per day                 Divide by (5 divided by charges per day).

This is given as an example on the table for Magic Item Creation, with the boots of teleportation, but that's a completely different effect, teleport being an instantaneous spell. But from the designer's point of view, they are both spells of similar level and both cost a spell slot to cast, so the effect doesn't matter a whole lot and they are priced similarly.

So this leaves us with 60,000 gp divided by 5: 12,000 gp.

That's the price for boots of speed.

However, to be honest, the rounds per day effect could use some standardization. Many magic items that use rounds-per-day effects are priced higher than other items of a similar spell level.