In 1998 maybe, though 1 hour at even 48kbit/s is 20 megabytes, which is a decent-sized program's source. (The Linux kernel source in 2003 was about 25MB, compressed.)
But in 2004?
But in 2004?
And remember, if you wanted to customize something you'd usually need not just one program's source, but also the libraries. Downloading all of Qt and most of KDE to customize something and build it from source took a loooong time.
Ubuntu's first release, IIRC
So even if you were willing to spend 10% of your monthly income (which is impractical, but this is an extreme example), it could buy you maybe 1-2 gigabytes of data. Or you could just, you know, order a (source or binary) CD for free or almost free.