The text mentions SACRIFICING power for the threads....this seems prohibitively excessive, in that I don't know of any players who would throw away good power for a one-off bonus...I certainly wouldn't sacrifice say 10pts to get a one-time 5pt spell damage buyoff....I'd just spend 10pts buying off damage at the time and then recover it later by resting...
Perhaps it would be better to change this so you don't have to sacrifice to the thread again when you re-embroider it.
e.g. Bezalel takes to wearing Robes. He finds, that while he can avoid most melee damage, he gets slapped around with spells too often for his own liking, so, hearing about these embroidery things he heads off to see Artemus to get one (no point going to a second rate hack when you can get one from the lord of threads himself - shameless plug). He sacrifices 10pts (plus whatever the cost of the service is - if any - a night with Mr's Fang perhaps? Expendable power?) and gets himself a 5pt spell damage sink.
Some time later, he comes to blow's with a couple of priests and gets a nasty spell thrown his way and decides to use his sparkly new thread to avoid taking any unnecessary ill-effects). The thread does its thing and then promptly becomes inert. After some appropriate looting and strutting about Bezalel heads back to Artemus and gets it re-tailored (or whatever needs to happen) paying any subsequent costs. The obvious benefit of this way, is that he doesn't loose 10pts of power permanently.
Alternatively, and this may have been the original intention, the character just sacrifices expendable power.
It costs expendable power to make these things.