"after that is buying IP addresses from other companies who suddenly
find that they don't really need all the addresses that they are using
(because they have all their desktops behind firewalls instead of
exposed directly to the Internet like they were in 'the good old days')"
No kidding. One thing about the IPv4 exhaustion is that the allocations
are extremely sparse. There must be a huge number of class C
allocations to small businesses which ony use 10 or so unNATed addresses
each. The rational thing for the ISPs is to start squeezing all this
sponginess by providing such price breaks.
What is very unsettling about this situation is that it's a preview of
what will hit later this century with respect to fuel, and even more
ominously, water. So far, the "free" market hasn't handled it so well,