Most of the ebay sports card sellers aren't old enough to remember the pre-eBay days when it was difficult as hell to sell cards. You had to put an ad in SCD or set up a table at a show. If you came to the show as a customer to sell cards to a dealer at a show, you'd only get 50% (if you were really fortunate) from those dealers.
Now, it's so trivial to sell cards !!! So, as a relatively NEW low-end, low volume seller, I actually like eBay !!!