Actually, I find very few "X-factor" coins at Whitman and FUN because I spend much less time canvassing the floor for such items, and much more time trying to make sales to cover the expenses.
Yes, if you are a dealer and the IRS accepts you as a dealer and not a hobbyist, then the table fees, lodging, meals etc should all be deductible expenses.
I would think that's the case...who would get a table at a conference if they aren't a dealer ? Those of us in the hobby are going to be walking the floor.