How to price subscription item based on the existing lines on the subscription?

We have group of products usually categorized as a bundle. The character of this bundle is in such a way that if any one of the product belonging to the bundle is ordered then the remaining products in the bundled can be ordered for free, For example Product X,Y, Z belongs to bundle A. If customer places an order for product X at a price of $200 and if the customer wishes to place another order for product Y,Z anytime during the subscription period, product Y and Z should be priced at $0.
Can you please share any reference material on how this can be achieved