One of my friend asked me the question that why deleting the Channel is not freeing up the space in RHN satellite.
I have faced this issue earlier as well. This happen because depending upon the type of channels packages are shared between the channels.
Taking one Random example.
RHEL 5 Channel and RHEL 6 Channel can have shared packages which are accessed by both channel.
Now if we are deleting one channel that action will not removed the shared packages, this will remove only unique one that means which belong only to channel which we are deleting.
Below is the redhat article explaining the same thing.