Best practice for managing (purchase cost of) a bundle/kit

[Robubble]

I'm not sure if this would be a feature request or if there ways to do it already.

How would you enter purchase costs of assets you bought as a bundle (like RAM kits or bundles that include multiple devices, you wouldn't call an accessory)?

I had two ideas, both with flaws:
Entering purchase costs to both items would falsify the total calculation, splitting the price across multiple assets would be a possibility but not really if the products can only be bought as a kit, I guess.

The Predefined Kits didn't make much sense to me yet as I can't bundle specific assets that way, only models. Also it wouldn't solve my problem with the puchase costs.

Maybe custom fields with a bundle ID and the price is only on the first (master) asset could be a way and bundling them by checking out all assets to the first (master asset)?