The multipliers are (almost) exactly what I suggested in the original post ( I made the long durational cast multiplier 30% instead of 50%). Here they are again:
Temporary Item classes:
0. A single charge temporary item is (100%) of base cost
1. Alchemical potion should be (80%) of base cost - harder to use than temp items.
2. Self only Scrolls should be (120%) of base cost - rarer
3. "Other" Scrolls should be (80%) of base cost - harder to use
4. Getting long durational spells (11 day/43 day casts) would have a cost: (30%) the base cost
per day vs per week/multiple charges
5. A 1 per week item should be worth 500% the base cost
6. A 1 per day item should be worth 800% the base
Additional item charges each cost (75%) of first charge
All items have a number of dragons equal to the level/rank of the spell added to their price.
Permanent items have an additional fixed cost: 3 gold - (the cost of ensorcelling/empowering a trinket?)
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The base values were created just as a starting point and need discussing. The principle I used was that there would be a jump in price at rank 5.
At Rob's suggestion I reduced them a little from what I suggested in the original post to what you see in the tables. Perhaps a little too much.
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Re item access I don't think we need more than 2 tiers of prices if we are restricting access to them anyway. Do you agree? One for common spells/invocations and one for rarer spells/invocations with guild restricted access.
tier 1: standard/advanced magic, standard path
tier 2: additional spells/primary school, sect/specialist sect (guild members only)
Primary school can buy items of their school at tier 1 prices. By the same token sect members should be able to buy items of their own sect at tier 1 prices.
*I think it would be better to make purist items harder to acquire rather than more expensive. How about purists can buy purist spells from their own school at standard prices, and only primary school can buy them at tier 2 prices, so in your example a battle purist won't be running round with fire purist items that she bought.
Here are item costs for tier 2 items with them costing 50% more than standard ones.
Screen shot 2014-10-28 at 09.54.34.png
(the formula adds a fixed +1 dragon so they always cost at least one more than the equivalent standard item).