If I eat sushi in Antwerp, I always think of Kaiseki. There are a lot of sushi restaurants in Antwerp but for All You Can Eat I choose Kaiseki, because it's cheap and it's delicious. I won't say it's perfect, because it's true sometimes the food taste nothing. Because the rice doesn't have a nice flavour. But I like the grill, I like the Teriyaki sauce. It has an excellent service, and it's quick and it's sure enough.
I think it's fair to charge you when you leave sushi and ofcourse you can't 'take-away' the sushi, because the price you pay for all you can eat is already cheap. And if you want to take away, it probably cost them a lot.