Ask HN: How do you implement business rules for product assortments and tiers?

Hi, Assume you have an application with bronze, silver, and gold "tiers" for which you charge $1, $2, and $3 respectively. Let's say you can click on one button with bronze, two buttons with silver, and three buttons with gold. Do you hard-code these business rules, or do you use a rules-engine? What is your go-to way to implement things like trials, discounts, etc. in the product? What is your go-to way to fragment all the features into a feature grid/matrix and grant/deny/limit/meter access to any given feature on the fly? Do you have successful examples using rules engines for that? Thank you, Previous submission with no discussion: https://news.ycombinator.com/item?id=28454775