The only thing that is actually copyrighted is the actual pattern itself. You can't copy it, call it your own pattern or design and sell it under your own name. . . much like a book. I can't copy a book and publish or sell it under my own name. However, I can tell the story of it to anyone I want. I am a retired musician. Music copyrights are like this as well.
So yes, you can buy the pattern and make the quilt and sell it. However, you can't copy the pattern and give the copy to someone else without the copyright-holders permission. If they allow you to copy it a few times, great. Otherwise, if someone else wanted the pattern you'll have to give them yours or they'll have to buy it. But again, the resulting quilt is yours to do with as you wish.