just a comment as i've done a few trade shows in my time. If your T.O. based your costs to do the show could be half those of out of towners, they get hotels x number of staff x four nights x associated meals (show food retarded pricing) x logistics to get booth in and assembled. A 10 x 10 booth can be 8-10k all in pretty quickly.
Its hard to calculate tangible sales vs. marketing exposure, this is why these shows will continue to downsize in this economy. Diluting the puddle by having multiple shows just makes it worse.
The show organizers start to offer incentives to fill floor space, even free booth space to charities and clubs, but then they don't have the cash input to promote the show and offer the value added like live bands at the beer tent ect. and now we are on the slippery slope, and the shows get smaller.