My used '05 came with one key - went to the dealer for a replacement.

1) Retail is about $260 - wholesale was $169 as I run a garage/car lot.
2) Took 30 days to get it after the order - required VIN from car.
3) Key was cut and started car as it was received - however, remote control for door locks did not.
4) Programming remote was $42.50
I do believe a key blank must be cut - and it is a MB style key that a standard key cutting machine cannot duplicate.

Hope your experience is better (quicker & cheaper) then mine.

Henry