Just an idea
in release of CentOS-3.3 in packages yum and centos-yumconf there is (centos-)yum.conf file with souch content:
for repositories baseurl=http://mirror.centos.org/centos-3/*
as I see from this: # host mirror.centos.org mirror.centos.org has address 69.93.142.19 mirror.centos.org has address 69.93.26.26 mirror.centos.org has address 69.57.175.50
So it means ALL trafic goes to centos.org
From what I understood, mirror.centos.org is round robined to all mirrors as it is. So I fail to understand how the costs are so high now.
Not just to three hosts (as I understund in main centos site).
It means ALL default (with non changed yum.conf) installation downloads updates from THAT three sites.
It also means that if there is 5000 CentOS machines and they run "yum update openoffice".
The generated taffic is 297065319 bytes * 5000 = 1.485.326.595.000 = 1.5 T !!!
( -rw-r--r-- 1 root apache 218087418 zář 16 14:42 openoffice.org-libs-1.1.0-16.14.EL.i386.rpm -rw-r--r-- 1 root apache 43240115 zář 16 14:41 openoffice.org-1.1.0-16.14.EL.i386.rpm -rw-r--r-- 1 root apache 35737786 zář 16 14:42 openoffice.org-i18n-1.1.0-16.14.EL.i386.rpm )