I've become a big fan of Pellegrino since I've been sober as well. Part of the allure is that I'm treating myself to something nice, and I'll have a bottle of it with a nice dinner the same way I previously would have treated myself to a more expensive bottle of wine with a good meal. I think their marketers have me figured out by pricing it the way they do! Oh well. Better for me to be duped by them than by purveyors of alcohol.
That said, there are cheaper sparkling water alternatives out there that I substitute now, and I can't really tell the difference. My grocer sells a cheaper option that still has the fancy packaging that I'm a sucker for at about 2/3 the price.
As an alcoholic I viewed my drinking as a reward, and it's been refreshing to discover that there are many nonalcoholic options that I can approach the same way (I've also become a fan of spicy V-8).