Invitation Design

when someone asks me to design an invitation, I want to start giving them the option of choosing from a selection of pre-designed templates, as opposed to designing invitations from scratch. any opinions what i should charge for this?

Are they templates that you designed?

yes, i designed them specifically for this purpose

I think you could charge a flat rate based on the time it took you to design each template, like charge for that hour (or2?) plus the extra hour of tweaking…
Doesn’t matter that you’re not doing it again for them, they are getting the same value.
and you wouldn’t be charging loads extra just to pump it up to make it worth it because you’ll get that fee each time…
so sort of balances out
hope that makes sense, good luck!