I would really like to see a comparison between this flat fee per "unit" (in this case users) model vs tiered pricing based on the number of these same "units",

I would really like to see a comparison between this flat fee per "unit" (in this case users) model vs tiered pricing based on the number of these same "units", where the "unit" is one that will be predefined and remain mostly static. So in this case, something like "$15 per user" vs "$39 for <= 3 users, $99 for <= 10 users, $249 for <= 30 users". Can anybody share such a study?