Ring of Wizardry I,II,III,IV,....IX?

[shadyizok]

I think combining Rings of Wizardry is a case of combining multiple similar abilities rather than multiple different abilities. Doubling 1st level spells is pretty similar to doubling 2nd level spells I would think.

Multiple Similar Abilities
For items with multiple similar abilities that don’t take up space on a character’s body use the following formula: Calculate the price of the single most costly ability, then add 75% of the value of the next most costly ability, plus one-half the value of any other abilities.

So a Ring of Wizardy 1 & 2 ought to cost 55,000gp, with it costing 35,000gp to upgrade a Ring of Wizardry 1 to also double 2nd level spells.

Yes, but if you read the text carefully it says: [..]that don’t take up space on a character’s body[..]. Rings take up a ring (finger) slot.

If you then read on:

Multiple Different Abilities
Abilities such as an attack roll bonus or saving throw bonus and a spell-like function are not similar, and their values are simply added together to determine the cost. For items that do take up a space on a character’s body each additional power not only has no discount but instead has a 50% increase in price.

And

A creator can add new magical abilities to a magic item with no restrictions. The cost to do this is the same as if the item was not magical. Thus, a +1 longsword can be made into a +2 vorpal longsword, with the cost to create it being equal to that of a +2 vorpal sword minus the cost of a +1 sword.

If the item is one that occupies a specific place on a character’s body the cost of adding any additional ability to that item increases by 50%. For example, if a character adds the power to confer invisibility to her ring of protection +2, the cost of adding this ability is the same as for creating a ring of invisibility multiplied by 1.5.

So we're back at +50%.

Personally, I don't think the price should vary depending on how you did it. I would just charge you the difference in price as you enchanted it -- i.e., a ring of wizardry I & II would cost 70k gp (40k +1.5*20k), so to go to that from ring of wizardy I would cost you 50,000 gp.

I agree with this. Same as when you upgrade your +1 sword to a +2 sword, calculate the regular market price (the cheapest possible) and subtract what you paid for it allready.
Maybe you could make one ring that takes up both your ring slots (think big signet with two rings attached on the under side, going over your middle and ring finger) and reducing the total price by 20%. That would make your ring of wizardry I to IV (295.000*4/5)236000. That is a bit more affordable. Or remove the most expensive 50%

BTW there is a series of articles on making magic items here: clicky

 

[Halford]

Ah, good point well made Sir. I shall consider myself soundly refuted!