Magic Items pricing

[mirtexxan]

Hello,

I'm reading very carefully the DFRPG Magic Items source book (which is also part of the DFRPG Companion 1) and I'm trying to find the reasoning behind the pricing choices. Most choices come directly from previously published material (the DF line of products, and Gurps Magic). Some of them seems to be imply completely new enchantments, such as Corrosive Weapon, Holy Weapon etc. (but unfortunately there is a bit of inconsistency here and there*).

However, I'm wondering... are the rules for creating Casting Items, and in particular items with Uses per Day (p.11) and Charged Items using the Charged Item Tables (p. 15) completely new, or they come from some other source? What's the design principle behind them?

Can they be derived from some application of Gurps Magic, or similar?
I can clearly see that "non rechargeanble" charges come directly from an adaptation of the "Spell Stone" spell in Magic to Dungeon Fantasy.

But doubling the cost for rechargeable ones (see again the table at p.15)? It is an entirely new rule or am I missing something? Unfortunately this seems to be different even from the Power Reserves on DF8, p.47-48.

My opinion is that the rules in Magic Items are a mashup of the rules in DF8, and the ones outlined by Kromm for using Spell Stones to create charged Items in Dungeon Fantasy, as they uses the same "10-energy points max" rule.

What do you think? Can you help me understand all of this? I know that it is not needed for DFRPG, but I'd be really curious to take a look under the hood!!!

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*As an example, the "Five-Gallon Canteen" at p.8 costs $4,810 and is a Charged Item (with the Create Water spell) with Limited use per days (5 charges). According to the rules given later in the book, this should cost a base of $4000 to enchant a Casting Item (a canteen worth $10) with Create Water, plus 5 Charges, each requiring 2 FPs. According to the table at p.15 the charges should cost $320x5=$1600, for a item total of $5,610. However the item is priced using the FIRST column in the table, for a non-rechargeable item ($160x5=$800) for a total $4,810. I guess that the fact that the item is limited in casting the spell only on itself may warrant the discount...