Vendors at stitch festivals pay to rent booth space and often also pay a registration fee to the organization running the show. These fees can run into hundreds or thousands of dollars before all is done.
If one is doing a consumer show, the vendor also has to file for sales tax collection in the state in which the show is held and also must file a tax report and send in retail sales taxes collected to that state's sales tax office.
What the vendor earns at the show is the vendor's.
There are penalties to the vendor who withdraws from the show at a late date or after the allowable cancellation date - - a percentage of the fee paid is lost.
There also are contracts and penalties for both sides - - the vendors to the organization and the organization to the convention center/show facility.