Per bob haller:
Since starting to pursue this, I have been wondering if each key's transponder has it's own ID number and, if so, if the vehicle's computer stores them.
It is starting to sound like "Yes" on both counts.
Suspecting that the cloning process is over-priced ($60 at the local hardware store), I priced the device they use: "Ilco EZ®-Clone" and found $2,400.
$2,400/$60 = Breakeven at 40 keys.
I call that a pretty good margin.... a ripoff, even - considering that they decline to cut a transponder blank unless the customer also pays for the cloning process.