From the website:
Use Promotional Code BOOKTHEMOUT To Receive $15* Passenger Fares
Kangaroo Island is a beautiful natural habitat that has experienced devastating bushfires.But the message is clear, we are open for business. We want to show you what KI is all about and there is still so much to see, do and love.
SeaLink has joined a campaign to encourage visitors back to this amazing island to help support the local community get back on their feet.
To help, we’re offering $15* passenger ferry fares so you too can show your support by visiting the Island with family and friends.
Book from 19th January 2020 to 29th February 2020. For travel from 19th January 2020 to 30th June 2020.
So come on, what are you waiting for? Book Them Out!
Use the promotional code BOOKTHEMOUT to receive this fare.
Terms and conditions: New bookings only. Not available during the KI Racing Carnival (20-23 February 2020) and Easter Long Weekend (9-13 April 2020). Available for sale from 19 January 2020 until 29 February 2020 and available for travel from 19 January 2020 to 30 June 2020. Ferry fares can be purchased without a vehicle booking. No minimum night stay required. Cannot be used in conjunction with any other offer or special eg Entertainment Book Voucher. Can apply to adult, child, concession or student fares unless standard fare is cheaper.
The vehicle fares are unchanged - $98 one way. KI Connect is cheaper if you don't need to bring your vehicle over. However, if you want the convenience of everyone and your vehicle travelling together, there is this option now with Sealink with discounted passenger fares. Or you could have all the passengers travel via KI Connect and the driver + vehicle via Sealink for the cheapest option.
So from a quick search seems to say $49 is a normal fare? Car $98.