Yes of course, if you have a CEO of a well know blue chip company speaking, you can justify charging more as attendees get to 'rub shoulders' with this person.
I'd say have different ticket types such as Public Sector, Private Sector and the Graduate
The most expensive being private sector and the cheapest being graduate.
It's difficult to suggest a price however an example could be:
Private Sector: £70
Public Sector: £40
Based on this you'll be able to increase your prices year on year, however you will need to revise this should you not have 'star' speakers. Your marketing will be important as you'll need to communicate to the consumer the benefit of coming to your event and what they can get out of it, this way you're justifying the cost earlier rather than later.