Perhaps from a legal standpoint. However, I have seen lots of pattern creators say that they are selling a pattern for personal use not for sale of the end production item. It's the same as purchasing a dress made by a designer, taking it apart and then using the dress as a pattern to repro and sell.
The right thing to do isn't always protected by law. Purchasing a design and selling copies based on another person's intellectual property, even if that property isn't protected by law, is extremely unethical. I respect creators too much to do so.