Suggestions on How to manage Productions Costs for Products?

Hello,

I need to record production costs for various products we are selling. Our business is involved in trade show organising so we generally set up a new Price List for Every event. As such, the only way I can think of to effectively record the production costs of products within a Price List would be to add a new field to Price List Items - which I see cannot be done. I don't want to record this on the Product entity as I do not want to update the costs retrospectively and adding a field to Opportunity Products would either require a lot of manual inputting or a whole sea of workflow.

Has anyone out there found a solution for this?

Cheers

Oli