Copied from the healing effects thread:
I'd give it a base complexity of the number of stress the consequence in question can absorb and say that, for the duration of the spell, that consequence costs 2 Fate Points to invoke or compel (you only get one FP back from the compel, but if it's a character doing the compel rather than the GM they pay 2). It's still there, you're not healing anything, it just doesn't bother you.