So if it was made by someone else, then you'd let him take Mythic Toughness?
Why should one line of mostly-unimportant backstory give or take 4 Refresh?
If it were made by a sponsor who had an agenda, limiting it's use and enforcing compels and restrictions on the player character; then yes, I'd be far more likely to let someone take Mythic Toughness for -1 refresh (which is what the cost is when you factor in rebates for the Catch and Item of Power).
And the mostly unimportant backstory is part of the reasonableness test. If players bought powers simply because they could afford them, any player with the free refresh could buy Physical Immunity to mortal magic at -2 refresh (-8 total cost, +2 for an Item of Power, +2 for protecting against one thing, +2 for "not magic" being easy to come by), Beast Change and Supernatural Strength for -1 (-5 initial cost, +2 for an Item of Power rebate, +1 for Human Form, +1 for Involuntary Change [with a condition on the change of something like "when I'm angry," it usually won't even matter that it's involuntary]), etc.
All of that is fine if the character has a valid reason in their backstory, complete with the Aspects and restrictions inherit to such arrangements, to have those Items of Power; such as being the emissary of some old god who hates mortal wizards or being a favorite of Thor gifted with an Amulet of the Berserker. Saying, "I made myself a jacket that puts my toughness on par with that of an ogre," is not a valid reason in my opinion. As I stated above, what's to stop a character who was allowed to do that from "making" more such Items of Power for himself or other players.
By allowing him to make himself an Item of Power giving any Toughness power, you're already ignoring the rules. By limiting the level of power granted, you're minimizing the impact of that. I'm just trying to prevent him winding up like the guy who posted a while back asking for help on how to reset his whole campaign because he let his players become too powerful.
Always on item? What's that?
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Typically proof that someone doesn't have the final version of the rules. Or didn't read them.
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I think by "always on" he means that it doesn't take conscious effort to activate--like the armor in Harry's duster.
What Mr. Death said. Plus, I actually only have the final version of the rules. I'm aware that there was a pre-release copy that had rules providing for creating an item which is always on (something about halving the effect, I believe?) but that's only because someone mistakenly copied and pasted from the wrong PDF one time. I'm glad that they took that out, because I could see how overpowered it could become with refinements. If I'd never read the final version of the rules, I'd have just suggested he use the aforementioned, no longer in the rules, method.