i dont know the formula but i give you an example:
so you talking about a fireball cannon. so if you want this "new fireball cannon" to be upgradeable and it should lose range but therefor doubling the damage we have a "new Magic Cannon". But instead of having 3333g you only need 2200g. also you start with a higher range which is a big benefit at start. sound a bit OP for me. but to make it clear, im totally ok with the idea... its all about balancing
so you talking about a fireball cannon. so if you want this "new fireball cannon" to be upgradeable and it should lose range but therefor doubling the damage we have a "new Magic Cannon". But instead of having 3333g you only need 2200g. also you start with a higher range which is a big benefit at start. sound a bit OP for me. but to make it clear, im totally ok with the idea... its all about balancing