Jason,
If you search for Marketo's B2B benchmarking study you should be able to get some idea after you answer the questions.
My experience is that events are almost always the same if you are running content and not just a Company Buy Us Now event.
Invitations: Opens 10-25% depending on city and topic. CTR maybe 5-15%.
Registrations: 5-10% of reach depending on city and topic.
Missed Ratio: 50% unless you charge a fee in which case it'll be 30%. <--I expect this across industries.
If you aren't offering much in the way of real content, then expect a lower response rate. I used to run events where we showcased our capabilities by offering valuable economic forecasts. I suspect that unless you can setup your event that way, you won't have the same level of interest.