Besides price of copying a key, there is a limit on number of keys that can be active - vehicle computer kicks one out when you try to exceed that. So I let it kick out the worn key that came with my vehicle, giving me three good copies plus a plain key to keep in my wallet for the door.

The procedure for activating a key is in the owner's guide, which fortunately was in my used vehicle.

(I tried having a key cut to code by a good locksmith but he struggled, perhaps a dealer would have better equipment. Result doesn't seem better than the experienced person at a satellite location of that business achieved by finessing to reduce depth of cut. (Experienced locksmiths can do that.)

 

GM parts department will cut a key to the VIN. Last I checked for about $35.
What seems to be the problem? Do you really need more than 10 keys?