I'd be willing to accept permanence of a transformation for free in some cases... but I'd still push for the player to pay extra shifts for "authenticity"... again, making yourself into a wolf that's close enough to a wolf to fool a biologist is a lot harder than it seems... same goes for diamonds no matter how regular the patterns are... after all, not all diamonds are created equal. The carbon structure in diamonds has never been found to be perfect, and the flaws that occur naturally and in artificially made ones are easy to spot with even a skilled optical inspection- the artificial ones stand out, and are considered less valuable (because they're less rare, and the value of rare minerals is almost entirely a result of their rarity).
Make one too regular, too unflawed, and you're likely to get a lot of unwanted attention.
Make it flawed the wrong way, and it loses value, or worse, mimics a variety of conflict or blood diamonds.
Litmus test: one could also use a ritual like this to turn a bunch of lard and canvas into a forgery of a lost van gogh oil painting. If the only defining factor in the shift-cost of the spell is the value of the item, then someone like harry, with no knowledge of art or forgery, and little eye for detail, could conceivably whip up a perfect forgery (genuinely perfect) in no time flat from a picture in a book he got from the library.
This, I'd say, is inappropriate when the item itself bears a great deal of complexity he has no right to mimic so easily (textures, pigments available in the era, aging and cracking of the paint, etc, that he'd have no way of knowing, much less getting right).
If you make the authenticity factor (DC of determining whether the item is genuine) something the player gets for free during a successful transmutation, then you make imitating a van gogh as easy as imitating a child's fingerpainting.