where do the cheap SLRs come from?

People,

This question may have been asked before, but I still do not understand
how 
come that brand-new SLRs (and probably other cameras) are considerably 
cheaper on eBay? The salesman at a photo store said with a touch of
disdain 
that all cameras sold over the internet are "grey market" and never come 
with a warranty, even if one is promised. Well, what about sellers dealing

in photo equipment and having feedback ratio close to 100%?
For example, I can get a Canon 40D with 17-85mm ISU + some extras at
1475.00 
Canadian, while the guy in this quite reputable store asks 1688.88 for the

same set (with no extras)? And this shop-boughten camera is made in
Thailand 
anyway.

Is there a difference indeed?

Big thanks ahead.

SB