Do you have the same exact hardware that the article is using? Otherwise, we can't say one way or another on that with the data you've provided.

I'm also pretty certain the article is benchmarking against the 10x copy file for the actual benchmarks.

See this example command in the article:

    time $PROGRAM <kjvbible_x10.txt >/dev/null

So, even if you had the exact same hardware, I'm pretty sure your program would only be a bit faster than the unoptimized C# version. However, it's possible that your machine is a lot slower than what's used in the article, and your program is actually pretty fast -- but without more points of comparison, we just don't know. You haven't run the other benchmark programs on your hardware and posted the results.