A friend of mine has a similar type of software where he is somewhat of a middle man. He charges the company $x base + y% of the transaction. His customer is

A friend of mine has a similar type of software where he is somewhat of a middle man. He charges the company $x base + y% of the transaction. His customer is required to have their own merchant account and his service just processes through their merchant account. The $100 would never run through his account. Depending on the nature of your business, another idea would be to charge a convenience fee to the exhibitor, but having exhibited at tradeshows for many year I would find that annoying. However, it wouldn't stop me from exhibiting. Annoyances are par for the course for anyone who has ever exhibited at a tradeshow managed by someone like Freeman. If a customer is shocked that they will only receive $95 of a $100 transaction for the value you add, then it may be time to re-evaluate how you communicate your value or find a new customer.