Create a custom line item

Hi,

I am using commerce 13.21 (Foundation), there is a scenario where I have too add interest as a line item for certain orders. 

Example: 

LineItem 1, SKU 001-001, Qty 2, line item price $5, line item extended price $10

LineItem 2, SKU Interest, Qty 1, line item extended price (based on internal logic)

I am planning to add a variant in the catalog with "INTEREST" as SKU. And then add a meta field "IsInterest" on the lineitem, and then override the DefaultLineItemCalculator's CalculateExtendedPrice method to check for the "INTEREST" lineitem and compute it's price.

Is there a better approach to this?

Regards,

Siddharth