I think Sushi & co offers the best value for money in Milan when it comes to all-you-can-eat sushi. the menu is 19.90 euro, not including drinks and desserts, and it has some limitations: some dishes (marked in green) can be ordered only once, some others (marked in red) can not be ordered at all unless they are paid separately. Honestly I believe these limitations allow the quality of the food to be quite high (of course if you can order king prawns without limits at 19.90 you might question their quality...). I found about this restaurant here on tripadvisor while I was looking for a cheap place where to hold my birthday dinner party, and being it quite close to where I live we've ended up going there all the time now!!