(I apologize, it's getting late, so what posts I manage from this point may end up a bit perfunctory and/or disjointed)
The Fate Point cost is determined by the refresh value of the powers granted. In the absence of a house-rule, granting greater levels of Toughness powers requires greater expenditures.
Even whether the discount from The Catch applies to Fate Points spent for access to Temporary Powers is up for debate. Even if it does, it would require an 'only protects against X' Catch to render Mythic Toughness into a 1-FP Temporary Power.
No problem about it. I was tired going off the Catch powers/costs from memory instead of re-reading the RAW. Catching errors like that is part of the reason I want others to review some of the prior to including them in the various DFRPG resources.
Anyway, here is the re-revised Coat of Toughness spell.
Eric Holt's Coat of Toughness*
This spell is intended to transform a coat of jacket into a protective garment which makes the wearer tougher than they would ordinarily be. At least for a little while...
Type: Thaumaturgy, Transformation
Complexity: 9+ (see Variations below)
Duration: A scene (about 15 minutes)
Effect: Temporarily provides the wearer the benefits of the power Inhuman Toughness (Armor: 1, 2 bonus boxes in the Physical Stress track, Catch: Water) at the cost of one (1) Fate Point.
Variations: The casting cost could be increased to two (2) Fate Points to have a Catch: Unknown. Or the coat can be enchanted to provide Supernatural Toughness (Armor: 2, 4 bonus boxes in the Physical Stress track, Catch: Water) costing two (2) Fate Points and with a Complexity 17, or four (4) Fate Points with a Catch: Unknown. Another alternate would be Mythic Toughness (Armor: 3, 6 bonus boxes in the Physical Stress track, Catch: Water) with a Complexity 25 and costing four (4) Fate Points, or six (6) Fate Points with a Catch: Unknown. Lastly the duration of the spell could be extended by increasing the Complexity and expending shifts to increase duration.
Notes: The effects of this spell stack with Supernatural Recovery powers, but not with Supernatural Toughness powers. It also follows the normal Armor stacking rules. If the garment with the spell cast on it is within a Circle when the Circle is closed, the spell ends immediately. Similarly, if the garment crosses a Threshold without the bearer being invited in, the power of the spell is immediately reduced by the value of the Threshold. If the remaining power is insufficient to sustain the spell, it ends immediately. At the end of the spell (whether duration is reached or something ends the spell prematurely) the garment which was the target of the spell begins to break down and disintegrate.
Much like what happened to Harry's coat at the end of Changes.
Lastly, the duration clock starts immediately after the spell is finished, not when the garment is first donned for wear/use.
-Cheers