Hm, strange. With Mathematica 10 and Mathematica 9 on Windows I get about 12.1 sec in all cases.
I'm using a local directory (I called it "C:\Users\arnoudb.WRI\scriptslowdown\") because my Documents directory is a network
backed directory, which can lead to slowness itself (you might want to see if you have the same issue, saving locally to a drive is
usually faster, especially when you are writing a lot of data (which is not an issue in this case though)).
