Cheapest I can think of is at Nippon Sushi outlets.
Plenty of sashimi variety including smoked duck. Very affordable and easy on the palate.

I'm no smoked duck connoisseur, but I think it's good. Bite size smoked duck is so easy to eat in one bite and I can definitely taste the smokey flavour. They also dab abit of sauce, which I think is mentai that adds more zest. I can guarantee its better than Sushi King.