Well, congratulations on your new MINI!
I'm curious about the $30 charge for the "beer can" exhaust tip, as you are correct, it is standard design feature of the MINI. Perhaps you got a different type of tip and they mislabled it in the package?
For clarity, the standard "beer can" exhaust tip is shown below. If you got something different, can you please post a picture?

(Perhaps it's an official MINI accessory?)
But if you got the standard tip
and they charged you for it, I would guess you'd want to have a word with the dealership about that.