Hi Mick - IME it can be all of those options.
Our private club slipway is £5 per launch for visitors in an honesty box or free to members @£20 per year.
Orkney Harbours charge £65 for 6 months usage permit (1 May - 31 October) in 2013 for use of all their slipways, moorings and berthing in harbours for small non-commercial boats up to 10m using them regularly:
Port Services | OIC Marine Services
For visiting boats it's £16 for 4 days or £32 for 14 days for the same.
There's usually free parking too by the slip.
But from experience I think ours are some of the cheapest - I'm off to the Western Isles next month and their prices are more than that... But still much cheaper than I find in England.
Hope this helps