I started collecting cels in 2001 because I was
a big fan of the Tenchi series (which I caught
on the Cartoon Network) and, like you said,
found some relatively inexpensive cels on eBay.
I also liked the idea that I was collecting
artwork (kind of like a museum) and the idea
that my cels were part of the production process
of stuff I was seeing on TV.
Of course, I didn't really start dumping a lot
of money on cels until after I bought the Oh! My
Goddess! DVD. :)