Surely this can be expected for our first Champions League game at the Juventus Stadium? Hard to know exactly how much fans are willing to pay, and Shaktar are a strange team, as they're always quite strong, but not from a prestigious league.
I would hope that whoever's in charge of ticket prices is able to learn from this, and adapt the prices slightly.
If the prices were a bit cheaper, you could still make the same amount of money by selling more tickets. Filling the stadium looks better to everyone - fans, our team, oppononents, tv companies etc etc. I'd assume that they'll adapt the prices better for the upcoming games, and although I'm disappointed from the turnout for the Shaktar game, I'm not entirely surprised that prices were miscalculated.
Edit: Just to add, the comparison with the other teams in champions league is probably quite unfair atm, they've been playing in their stadiums for years in that competiton, and have had time to figure out what prices work etc.