ebay and kit shows both have their place in this hobby. For the sellers, shows are a great way to quickly clear out some stuff and ebay is a good place to get the most out of a sale, if you let it sell at a fair market price and not and inflated "buy it now" price.
What irks me is when show sellers ask "that is what they are selling for on ebay" prices. My answer to them is usually, "then put them on ebay!"
For buyers, shows offer a great way to stock up on kits selling cheaper than current LHS prices. I know we should support our LHS', but when you can buy three kits for the price of one, all is fair. As for ebay, it is a great way to find some pretty rare stuff, but, be ready to pay for it if it comes down to that.
You mileage may vary!