A 50
Quote Originally Posted by powerdemon View Post
How would I go about figuring out the price to make it/to buy it?
You wouldn't. As there is no such item already, your DM would first decide if you could make the item, and then what the price would be. The DM would start the price determination by comparing the desired function to similar items in the game. (Determining a price by the spell formula is pretty far down the list, and it's against the RAW to start there.) As there are no such items in the standard magic items list, you probably would be unable to buy one.