This is a question lots of show organizers struggle with.
With all the pressure most of us have to drive non-dues revenue, the tendency to monetize anything and everything is understandable (I recall back in the ’80s when a certain show starting selling advertising on the front cover of their show guide!). But I caution my clients to tread carefully.
If you agree that your attendees are your most important and valuable asset (in my opinion, your exhibitors are more your partners than your customers – I’ll be happy to elaborate at another time if you’d like), then it’s important to make these decisions in the context of what is in their (and your exhibitor’s/partner’s) best interest. Sure, you can charge exhibitors for “enhanced” listings but think about what happens when you do that. There are many reasons why a company might choose not to purchase an enhanced listing, and one of those reasons is that they’ve already stretched their marketing budget to the breaking point. I would argue that depriving your attendees of any information that may be important to them is an unintended consequence not worth risking.
I would strongly recommend that you make your “enhanced” listing the standard listing that comes with the booth. Announcing that everyone will be getting enhanced listings at no additional charge beginning next year will likely be viewed as a good thing. And if you’re contemplating a booth price increase, it gives you something to point to as an offsetting benefit.