You will need to buy the Starbucks coffee machine which consists of grinder and espresso machine, Greenfields brand milk. If you buy another brand of espresso machine different from the one that Starbuck uses, then it won't be authentic anymore. A household type of machine would cost a few hundred up to thousands. For Starbucks I think it will cost more as their is meant for business.
Also remember to purchase Starbucks cup to make ensure it is Starbucks coffee.