the cost of carrying routes

Some ISPs charge for actual bits carried (peak usage, actual count,
whatever) in addition to or instead of per port/circuit charges.

Do any ISPs charge based on the number of announcements a customer
advertises?

If downstream advertisements became mainly smaller prefixes (say /24)
that were not aggregatable by you as their upstream ISP, would you
answer the above question differently?

-ron

Ron,

Many carriers require that you advertise a certain minimum number of
routes to them over your peering sessions, or they will not peer with
you. This suggests that those carriers see routes carried as a point of
value, rather than or in addition to one of cost. I have seen 5,000
routes as a minimum used by more than one transit-less carrier.

Is this really an operational value perception at these carriers, or is
it simply a means of creating a barrier-to-peering? Are fewer, shorter
prefixes seen as more valuable than longer ones, e.g. swamp /24s? Is a
University or other entity with a legacy /16 more or less valuable as a
peer than a growing ISP with a few /20s, and presumably more eyeballs
and/or content behind them?

i have related question to ron's (a bit hypothetical but interesting
nonetheless).

if isps charged for bgp announcements, would the number of announcements
that shouldn't be made (e.g., those due to configuration errors and poor
operational practices) go down?

  -- ratul