When your key requires a security detail, you know you've made it. At the NY Auto Show I found the prototype key for Koenigsegg from made by Optimal Innovative Solutions (same company that made diamond Rolls Royce hood ornament).
Key is made of platinum and black onyx circled with 40 carats of diamonds. Not a factory availabl option yet to my knowledge and no price was given but estimates put it at $250k USD
Link to their facebook