MMI cable comes standard as well as one set of carpet mats along with a First aid kit.. It is strange your new Audi is missing these. Maybe local dealer is selling it as an option to make extra money. Get in touch with dealer and ask for Mats and Cable. If they dont help send email to Audi customer support. They are very good responding emails.
The MMI is propriety connection cable. Original genuine cable cost around $80 while its available on ebay cheap aftermarket china made for $15. I dont recommend the Chinese ones as some features will not work. My VW use same MMI cable as Audi and i tried the aftermarket ones and steering controls were not working.
Original premium floor mats are above $150.