I took the ferry from Palermo to Cagliari, booked on Tirrenia, cost 132.47 Euro, expensive for a 12 hour journey. I actually paid an extra 20 euro for a seat without thinking, there was no need because you can sit anywhere and there are lots of places to sit, even in the so called Reserved First Class seats, no one checks and I should have known that having been on so many of these ferries. I also bought a meal in advance for 8.90 euro which is quite reasonable and this is worth it as you pay 20% more on the ferry itself. The ferry does not run everyday and it was quite full, so book early if you are in a car and want a cabin. I had to stay an extra day in Palermo because the next ferry was on Saturday but that worked out quite well.
The ferry departed on time at 1930 and arrived on time at 0730 the following morning and the sea was flat, did not even feel like we were moving. I checked in at 1730 and there was a long line of cars stretching out of the port and into the road, get there earlier if you are in a car. If you are on a bike you just ride around the cars to the front of the line and there were at least 30 bikes on this ferry.
Cagliari, capital of Sardinia and another ancient city. I had to get another SIM card here as the credit I had on my old one got used up when I was on the ferry, turn your Data off before you get on the ferry. Plus it was going to expire in a few days anyway so no great loss. The new SIM is valid for 1 month and cost 20 euro, 100 min of talk and 4 GB data. I should have bought the original SIM card for 3 months instead of 2 months but at the time I did not know that roaming charges would be abolished in the EU.