Hello, it can be sold like this, bundled and purchased separately. Here is the reference link:https://pixel-vault.itch.io/pixel-book-ui-v1
I don't know if I understand correctly but it seems like there's the bundle price and the individual items are on sale, but the sale is for everyone and not for who already own some assets of the bundle. The solution I think is to create different bundles with the condition of owning some assets to purchase, so I will look into that.