Maybe I missed it, but where is the crack and how noticeable is it? It is hard to tell with the dark pictures. You don't say what you paid, but if it was substantial, I would expect a well known auction house to admit their mistake and accept a return. A visible crack is more than a flaw.
For value, if it displays well, enjoy it. If you sell it, it should not bring more than 10% of the value without the crack. There are exceptions if the crack is visible only from the side and the paperweight is especially nice.