Link here to published prices - A or B tariff for TT period:

https://www.steam-packet.com/assets/pdfs...84af42a80b

The document normally lists motorhome tariff, but does not for 2018, if i remember correctly a 5.5m motorhome was the same price as a car & then you would pay £15 for every extra meter.

I paid about £370 return for my motorhome for 2017 TT

I do know commercial vehicles are charged more than motorhomes, but not sure of costs. I was once queried that my VW T5 was a campervan at check in - it was!

Interestingly, if you were to book Dover -Calais ferry (22 miles) for the peak period of July/August, then the cost would be around £200 return - making the Steam Packet cheaper by the mile! Plus you wouldn't get to see the World's Greatest Road Races for free....