When adding a buying value to a coin that you are adding to your collection if you type "0" or click the down arrow to set the value as "0" it does not save the buying value of the coin. You have to type "0.0" in order to get the buying value to save.
Not saying to add a default value. But entering a value of "0" does not work, but entering a value of "0.0" works if you want the value to be set to 0. Why can't you enter just "0"?