I’ve been thinking about this recently since I’ve been making a lot of pasta and I actually prefer the taste of Kraft parmesan cheese on a lot of things over the “real” parmigiano reggiano especially when it’s used as a topping eg. ceasar salad and pasta. I find that parmigiano reggiano has way too strong of a flavor and it clashes too much when eaten with other things.
I don’t know on what country/area of the world you are, maybe the two products aren’t equally available or have different prices.
Here in Italy, Grana Padano has a slightly lower price than Parmigiano Reggiano, and they are equally available generally in big and small distribution stores.
I like grana much more than parmigiano because it has a more delicate taste. The latter has a higher fat percentage and you feel that “greasy” taste which not everyone likes.
The price difference is due to stricter regulations in the parmigiano specification which should result in a more qualitative product (not only grass feed cattle but also from very specific regions, milk can be collected just once a day, no preservatives are allowed whatsoever, etc.).