If there is a chip or other security device in the key, you need to go to the dealer or a locksmith.
If the key has a chip or other security device and you get a $2 key from the hardware store, it will turn in the lock, but it won't start the engine. It may even trigger a security ststem and set off an alarm.
And $100 is the going rate for one of these keys. You are not being ripped off.