From a brief look Trenitalia seems about the same as DB. The express train Milano - Roma is 89 EUR. I think DB would charge something like 100 EUR for that. The travel time (2h55 for ~420 km) is impressive, I'll give you that. I wonder how many stops there are on the way -- not too many I'd wager.
Just last week I bought return tickets from Rome to Milan for the days around Christmas on Italo (the only competitor for high speed trains) and I paid under 50 euros return. Also the distance is not 420 km, but closer to 600 (it's 480 km as the bird flies). And regarding stops, you can get one that doesn't stop at all and it's 2h40 IIRC.
That's insane. In Belgium I could buy a `railpass` which is a 76€ piece of paper on which I can write ten different trips from any station in Belgium to any station in Belgium. Which basically means that any train trip in Belgium would cost you a maximum of 7.60€.
Belgium is only as large as Italy's Lombardy plus Piedmont, two adjacent regions in the north west. There is no Italian equivalent of a two region pass, but Lombardy has an unlimited monthly pass for all public transportation, bus, metro, regional trains, at 107 Euro, plus an extra 40 Euro to access fast national trains (within Lombardy). Given that an unlimited monthly city pass in Milan is 35 Euro, it's about the same cost of your Belgium ticket. It's for half the area but it's unlimited. Anyway, if we had a region the size of Belgium probably the price wouldn't increase much: people tend to travel close to home.