I would agree with you on this.
If you have a small marketing are its NOT a good idea.
If you only plan on one show a year...too much money to spend.
We are in a large market area and we still have people stop outside of our area. We then take their name and tell them that if we make our circle bigger we will notify them.
The other thing is we found is...you also get a lot of referrals from the people you get at shows.
For us its working great!