adwords sandbox authentication & api units

[eli...@gmail.com]

one question:
Is there a difference (in terms of APi unit billing) if I
authenticate on NS "https://adwords.google.com/api/adwords/v11/" using
sandbox headers?
To clarify:
I'm using sandbox service (i.e https://sandbox.google.com/api/adwords/v11/TrafficEstimatorService?wsdl)
but I authenticate (i sent headers with sanbox login details) to
"https://adwords.google.com/api/adwords/v11/?" * which is working fine
in regards to authentication (it will not authenticate me with
incorrect clientemail & devtoken when using sandbox)
Also, everything behaves as it should when working in sandbox - I have
bogus data returned adn i can't authenticate without using sandbox
headers.
However, I also have strange API units numbers (ridiculously high)
when bill comes in .

*I authenticate on https://adwords.google.com/api/adwords/v11/ NS
because https://sanbox.google.com/api/adwords/v11/ just doesn't work
for me (server keeps throwing an error that a 'email' nheader is
missing. Also, I couldn't find anything in docos that relates to
authentication name space.