'ROI' gets thrown around at trade shows without anyone actually doing the division. The formula is not complicated: total spend on the tactic, divided by leads it produced, gives you cost per lead — the same metric every other channel in your marketing budget is judged on.
This example walks the math with real numbers: a documented rental-cost range for badge scanners and adgamify's own published Event Pass price. Your own lead counts will vary by show size and traffic — plug in your numbers using the same formula.