If you go to the local show it is your time, gas, paying for the table and sale tax.
I agree on having to factor in sales tax, and the cost of the table. For me time and gas aren't factors for local shows. I do set up at the shows to sell, but there is also a social aspect to the show. (and I often buy a few things too) Many of the table holders know each other, as well as some of the attendees, and the folks operating the display layouts.
For me, York is a different story. When I go to York as a non-table holder, all the expenses are just part of the hobby. Same goes for getting tables at York with a group of people, so we can take turns looking around and visiting. (selling isn't the primary purpose of attending)
If I was to go to York myself or with my wife specifically to sell trains, I'd want to cover all my expenses.
