Having a Mercedes-Benz is one thing, but getting a custom-made key made out of solid 18-karat gold and inset with 300 cut diamonds for the luxury car is another. Made in Germany by Selected Jewels, Golden Key wants to do away with the standard plastic car key, because if you're buying an expensive automobile, you probably want a key to match. Available in rose, white and yellow gold, as well as platinum, you can personalize Golden Key however you want, from the type of gemstones used to the pattern. Since they're one-of-a-kind, the price really depends on your design, but it generally starts at €30,000 (around $41,616). Contact the company to set up a private appointment.