Pathfinder 1E Magic Item Pricing

[was]

...I'm looking for help pricing a minor magical item. Basically, it's a blank magical ring that becomes attuned to the first cantrip cast upon it. It then lets you cast that cantrip three times per day. Once attuned to a cantrip, it cannot be changed later.

 

[JoeElf]

Orange Prism (Ioun Stone), Cracked: Wearer adds one cantrip or orison (determined when the stone is created) to his list of spells known or spells prepared. Price: 1,000 gp.

http://www.d20pfsrd.com/magic-items/#TOC-Magic-Item-Gold-Piece-Values
Pricing magic items shows this on the chart on the
No space limitation = Multiply entire cost by 2; example =Ioun stone
So, take the 1,000 gold pieces and divide by two for using up a ring slot = 500 gp.

A wand with a cantrip on it costs 375 gp. You only get one spell, it has limited charges, but it has no restriction to 3 times in any one day.

Spell Effect: Base Price: Example:
50 charges, spell trigger = 375 gp = Wand of a cantrip
Command word = Spell level (.5) x caster level x 1,800 gp = 900 gp = Ring of a cantrip
Ring with 3 charges/day = 900 gp divided by 5 divided by 3 per day = 540 gp = Ring of a cantrip, 3/day

 

[was]

540 gp = Ring of a cantrip, 3/day

...Thanks for the thorough answer. I like your pricing.