I paid almost $300 for a spare key for my Land Rover. But I too will not go on trip without a spare car key!
I had to take my car in cause I was hearing some rattling. Loose fitting on the exhaust. Warranty and all that. Anywho I asked what the price was for a "Full Key" for my Corolla Sport XRS. Toyota's switched over to the keyless fob being integrated into the key. So you've got a chipped key with a keyless entry built in. For a set (They give you 2 plus 1 chipped valet key when you buy the cars) it cost $500.
I can see the obvious benefit of chipped keys. No chip, no signal and the engine stays locked.
But God help you if you lose your keys.