In fact, combining costs across your spectrum of shows allows for economies of scale and, ultimately, savings by sharing. I've always called this approach a Total Cost of Program evaluation.
Start with lining up your shows side by side on the calendar (for the year, January to December or 18- or 24-months out). Be sure to include all the things that contribute to expenses over the year:
- Space rental
- Exhibit house expenses (pull & prep, load out and in)
- Show-specific changes (new graphics)
- Show services (electrical, drayage, rentals)
- Warehousing (for the year)
- Supporting contractors
- Your travel (if it comes out of your budget)
- Repairs and major changes
- Capital cost amortization
Total things by row and column with a grand total at the bottom right (if you use an Excel spreadsheet like I do). That grand total is you total cost of program.
Now you can divide this by account numbers or departments or charge off to partners. Or, when reality sets in, find ways to combine shows or services, cut deals on multiple functions with your vendors or other cost cutting measure.
If you want a copy of the spreadsheet I use or have otehr comments, please leave a note in the comments space below and I'll get one to you.