1. I think I heard the appraiser say that in 1840 this blanket would have cost around $50-$60. That is $50-$60 dollars in gold backed currency. If gold has held it's purchasing power then that blanket, if produced today, would cost somewhere close to $5000. That is assuming that the wool, dye, labor and resources to produce it, as well as the effort to produce the gold that would buy it, are equivalent. I don't think they are.
2. The auction brought in 1.5 million dollars for the blanket. The auction value is not based on the value of the blanket as a good, but rather on it's historical value. The blanket was made before the treaty of 1868 which more or less started the end of traditional Navajo culture and began the "Westernization" of same.