A while back I as trying to find out about getting keys made as I lost mine. The ignition lock had been replaced so a vin to Mercedes was useless. I didn't want to spend $450-$650 on ebay for a replacement ignition lock and deal with the install. Called a local locksmith who ordered replacement blanks. He was able to hand cut a new key w/o removing my ignition lock and produced 4 more for a total of $75. I'm thrilled!!
How he did it: He filed the chrome off a key blank down to the brass. He then slid the key into lock turned it a few times until he could see an impression of the tumbler pins, filed to them and repeated until the lock turned. Cut fresh keys from his hand cut blank, I now have four. Other locksmiths I spoke with quoted hundreds for a the same result.