I've encountered some rather expensive fitted sheets. Unless you're insistent on this brand, why not do some checking at closeout specialists, like Tuesday Morning? I've seen some rather high end sheets there, made in France. They're marked way down from retail.
My only experience with Frette has been with bathrobes. I bought two of them a few years back, at COSTCO. Twenty-eight dollars each. They're luxurious and appear likely to last for a long time.