Why would you be shocked and stunned?
All main dealers know how to charge better than a wounded rhino but, Lexus being a luxury brand, they have refined the art to unprecedented levels.
It does beg the question as to why you didn't do said research first and why would you go to Lexus main dealers for a bulb anyway? I use main dealers only as a last resort or when it's something specific that no one else makes, such as an oil sump pan or something, but I would never even dream of using main dealers for bulbs, wipers, tyres or anything along those lines.