makes me wonder if these new details should also live in the database

Yes - they probably should!

Most of my sites have multiple environments with identical copies of the codebase except for a Variables.pm file that defines things like the DB instance to connect to, Stripe and other keys. Naturally, the Stripe price keys got put in there which is sensible when there are just 3 keys.

I was planning to extend what I already had. Then I realised that I probably needed a method in the common module for the site to return the correct Stripe price keys. Your observation that these are better stored in the DB really does make sense especially as a method is needed to read them anyway. It may as well just read the database!

Thanks you pointing out that to which I has cognitive blindness :)