Doesn't have to have sold gold.
Mei Francis has probably made several billion gold from all those traveler's tundras she's sold over the years. Not to mention the bears/wind wyverns, ect. Plus the justice badges/jp dumped on the wooly mammoths. Probably has pure gold houses made here and there.
I have bought the one from the OP on the BMAH. Only cost me 38k! Better than farming, which I did, over and over and over...