In the Grimaldi Lines site you can make a Online Booking and preview how much the trip would cost you.
As I'm going in the Peek Season (most expensive one) it says the ticket would be 80€ (full-fare), so a total of 64€ with discount.
This was what you paid? Because railcc says it's cheaper Barcelona - Rome than Barcelona - Livorno, and according to the site it's exactly the same ammount of money...
Can you tell how much you spent in this trip and what season you went (low, shoulder, peek) ?