You can get them at places other than the dealer. Try googling "transponder key".
Plenty of (non-dealer) places doing transponder keys here in Australia. Dealers were charging extortionate prices (I was quoted $500, was about 7-8 years ago) I think believing they had a captive market. All they did was invent their own competition by making it worthwhile for others to gear up to encode them. Still not cheap here though, typically $130 if you need one right away. If you don't mind a mail-order delay they are/were also available on eBay etc.