A little over two weeks after it announced receipt of "conditional approval" to open its $5.5 billion gigafactory in the town of Grünheide near Berlin, Tesla$Tesla Motors(TSLA)$ officially announced the factory's opening on Tuesday. Reports say that CEO Elon Musk literally danced in joy at the opening. Investors are pretty happy, too, because Tesla stock is up 3.3%. Why is this such a big deal for Tesla? As The Wall Street Journal explained yesterday, Tesla plans to grow its Berlin gigafactory to the point where it will be able to produce 500,000 cars per year -- but that's just one part of the good news. By building cars in Europe, Tesla will be able to avoid both the cost of shipping cars to Europe from plants in the U.S. and China as well as impor