That, is opening a large can of worms.... I would say it depends on the following factors -
Employer attitude
Area
Profitability of practice (big one in my mind, if a practice is making mega bucks they can afford to offer the high levels and therefore secure the best potential trainee)
Need for the employee i.e do they need that body NOW or just to fill a small gap in the team
Previous education level
Responsibilities in the role
In my experience, I know trainees who have started on anything from minimum wage too £7.50 p/h. I would say to my knowledge the average is £6.20 p/h. But I'm pretty sure that the next DN's personal experience will give you a different answer.
Hope that helps in anyway at all.