idk, I use Construct explicitly when I don't feel like coding, I don't think there was any other ways to do JSONs unless I'm just blind.
Think of JSON as a more advanced and flexible dictionary. It's not that complicated once you try it.
You can of course use a dictionary. There are two options:
1. Name the keys in the dictionary as CardType&ValueType, for example "DarkKnight_price":10
2. Create a new instance of the dictionary for each instance of the card sprite. Link it with the card (for example, by UID). Then each card will have its own dictionary.