Grams/serving means nothing. All they do to get those numbers is jack up the serving size. Most protein servings are based on 1/3 cup (the size of the scoop that comes in most buckets of protein). For powdered protein, that is about 25g of powder. For whey isolates, at least 22.5g (90%) of that must be protein.
Isopure is ion-exhcange whey protein isolate. While the ion-exhcange process does yield the highest percentage of protein (95%) per serving, it has its drawbacks.
I was surprised when I noticed the enormous scooper they use and that the serving size is two scoops. Don't be impressed with the 50g per serving. I think it is good quality whey however.