Let me see if I got this tier pricing thing correct.  Using the
logic presented if I own a grocery store and know that customer A
has a family of X number of people I should be able to charge them
price AX for thier purchases and for customer B that has Y number
of people in their family I should be able to charge them price BY
for those same groceries.   Umm.... I think my grocery store would
go out of bussiness.

  As far as software and tier pricing goes, I agree that if a
software product were to cost the vendor more based on the number
of users using it then those cost seem appropriate to pass on to
the customer.  BUT... what would make a piece of well written
software cost more based on the number of users?  Seems to me that
if a vendor is experiencing additional support cost at a site with
50 users versus a site with 1 user then maybe that software has
some 'features' that need to be addressed by the vendor.

   Just my 0.02 US.

   My opinions.