Upload file via .net C# API or Python is too slow compare to Web upload

I'm experiencing the issue that upload to box by API in C# or by Python is damn slow.

Upload from Web page I think > 10 times faster.

Anyone also experience this issue. Appreciate if someone can give me some suggestion to over come the issue.

Thank you very much.  

----

Im using 8 thread, for each thread I create 1 user token to send 3-4 files to same folder.

1 files size about 500MB