With Moto Maker, you can choose between four different Horween leather finishes, a bevy of colors variants, and a wood option. Choosing the leather and wood options will set you back £20 (around $32). You can also customize the sides of the device, and add a custom engraving at the back (although something like "Plonker" isn't likely to get through Motorola's profanity filters).
Moto Maker even lets you choose storage, with the 32 GB storage model costing an additional £40 ($64). Getting the higher storage variant is advisable, seeing as how there isn't a microSD slot on the new Moto X. Once you're done with the customization, you can email the finished design to yourself, and Motorola will send you a mail once the device is available for purchase. As for how much the device itself costs, the website lists a £419 price tag, which comes out to around $683 before all the custom options.
Proud of what you've created using Moto Maker? Show off your designs in our forums!