You could think like this, and you should if the rules would be fixed. However, this does not work like a smart contract and rules can and will be changed. If the amount of Stardust inflation from burning planets would go up too much, we could react and decrease the amount of Stardust from burning planets. We have fixed the amount at a level, which makes economically not very viable to burn too many - but if it becomes necessary we would adjust these levels.