Thanks a lot, sounds very reasonable! I got a response over email from the person mentioned at the bottom of the article Wild Coast Hike - Hiking South Africa, who told me that trail policy does not allow solo option.
They gave me some options for group. Could you give me an idea if this is the usual price list, please? I am not familiar with packages costs, so better to have a second opinion 
" Here are the options to choose from:
Wild Coast sun to port St Johns 8 days 7 nights R6000.00pp
Wild Coast sun to Mbotyi 5 days 4 nights R4500.00.
Wild Coast sun t to Msikaba 3 days 2 nights R3000.00.
Msikaba to Mbotyi 3 days 2 nights R3000.00.
Msikaba to Port St Johns 5 days 4 nights R4500.00.
Prices include:
Accommodation with bedding.
Meals.
Guides fee.
Ferries.
Nature reserve entrance fee.
Shuttle back to start point or trail head."