I recently had Fly Sushi here in Buenos Aires at a friends place and it was incredible. Not sure how much it cost, I'm sure it was pricey but there was a great variety and even the take out was presented beautifully.
Higly recommend Izakaya Niji
Have been in business for many years, I believe the owners are second generation Japanese in Argentina, delicious Japanese food and sushi. The best, the private room with the low table surrender by paper screens, feels like a little trip to Japan. Reservation recommend