As compared to what and where ... ??
It's pretty easy to say stuff like this ... with no baseline comparison around the world, in tons of different restaurants.
For instance, my baseline of eating in more than 125+ countries, different price points and styles of restaurants ... I can say that "higher price" tourist joints like La Brigada, Don Julio, La Cabrera, Duhau @ Park Hyatt are pretty damn phenomenal at 1/4 the price you would pay at any North American restaurant of similar ilk.
Is Argentine beef better than everything else in the world ... can't say ... I'm sure there is some sherpa who feeds his cows honey glazed berries and ambrosia and sings them lullabies at night to ensure they are never stressed - I'm sure that beef is pretty phenomenal.
What I can say, is that if you're in Argentina for a while, you're going to get some great beef and you're lucky to have the comparative price points you have. Don't think it's any better out there ... (Maybe I'm writing lots because I need to defend how positively I felt about my last couple weeks in Buenos Aires ;P)